The Late Empire | Roman Architecture | Second edition

The Late Empire  | Roman Architecture | Second edition

The Late Empire Part 1 | Roman Architecture | Second edition

The historian Dio Cassius wrote: ‘After the death of Marcus [Aurelius] history passed from a golden empire to one of rusty iron’ (Dio, 72.36.4). In ad 192, 12 years later, Commodus, the son of Marcus Aurelius, was murdered and there followed a brief period of struggle between several candidates. The final victor was Septimius Severus, born in Lepcis Magna in North Africa. His reign (ad 193–211) marked the end of the power of the great Roman families and of Rome as the centre of imperial power.

It also marked the beginning of a rigid state bureaucracy that was to control every aspect of Roman life. In art there was a break from classicism and the pompous official art of the Antonines; in architecture, the Severans were more active builders than the Antonines. The first task that confronted the new emperor on his accession was to restore a large area of the Forum between the House of the Vestals and Vespasian’s Temple of Peace, which had been swept by fire in ad 191.

He rebuilt the Temple of Vesta, the House of the Vestal Virgins and the Correa Vespasian, and reinforced the Clivus Victoriae with arches. While rebuilding the area a Marble Plan of Rome (Forma Urbis Romae) was prepared at a scale of about 1:240 (ad 203–211). Carved on 151 slabs of marble and measuring 18.10 × 13 metres overall, it was fixed to the wall of one of the halls of the Temple of Peace and shows the ground plan of practically every temple, bath, insula and street in the city.

More than 10% of the total survives, some parts showing quarters of Rome that are completely unknown today. It gives fascinating glimpses of streets lined with insulae and horrea of the Ostian type as well as the occasional atrium/peristyle house (Figure 12.1). Like Ostia, Rome must have changed profoundly in the course of the second-century ad and most of the sprawling private dwellings must have given way to tall apartment blocks.

The Late Empire  | Roman Architecture | Second edition

Perhaps the best-known monument of the Severan period is the large triple arch over the Sacred Way in the Forum, built to commemorate the emperor’s Parthian victories (Figures 3.4 and 12.2). A gigantic structure, 23.27 × 11.20 × 20.88 metres high, it was the largest arch erected up to that time and probably followed the pattern of some lost Antonine arches. Its position, on sloping ground at the foot of the Capitoline hill, added to its imposing effect.

It has also been noted that it was built diagonally opposite the Arch of Augustus (Figures 3.5 and 3.8), but was much higher and bigger, thus linking the emperor’s achievements with those of Augustus while suggesting that he was greater. The arch is finely proportioned with three passageways flanked by free-standing Composite columns on high plinths supporting sections of projecting entablature.

The inscription in the attic dates it to ad 203. On top of the attic was a massive bronze quadriga carrying the emperor. While the arch itself was conventional in its arrangements the sculptures rejected the Classical tradition and looked toward the late Empire. This is particularly evident in the four big relief panels above the side arches which represented episodes in the Parthian campaigns of 195–199 ad. The soldiers were carved as an undifferentiated mass, the folds of their garments indicated by the heavy use of the

Figure 12.1  Rome, Marble Plan. (After G. Carettoni, La Pianta Marmorea di Roma antica. Forma Urbis Romae [Rome: Comune di Roma, 1960], pl. LIII 453 a b c d.)

Figure 12.2  Rome, Forum Romanum looking NE. From left to right: Temple of Saturn, Column of Phocas, Temple of Vespasian and Titus, Arch of Septimius Severus; in the background, the Tabularium.

drill, while the emperor stood above them, a larger, more majestic figure. The Arch of the Argentario, dedicated by the money-lenders and cattle merchants to Septimius Severus is not strictly an arch at all because its passage was covered with a lintel, but it is an interesting and well-preserved little monument, 5.86 metres wide × 6.90 metres high.

Today only the sculpted upper part with its poorly executed reliefs is above ground. One panel showed the emperor sacrificing, while his wife had her arms upraised in the eastern manner of prayer. The composition was awkward as if the spectators were no longer glimpsing a real event, but something posed for their benefit.

Severan ornament is usually extremely rich, harking back to the Flavian period. This is perhaps because Septimius Severus made so many repairs and additions to the Flavian Palace on the Palatine. He completed the projected bath building and made massive extensions to the SE corner of the palace supported on concrete substructures which are still a conspicuous feature of the hill.

Travellers arriving at Puteoli (Pozzuoli) and Brundisium (Brindisi) would have reached Rome along the Appian Way which terminates close to this corner of the Palatine. The Severans were greatly interested in developing this part of the city, and no doubt with an eye to visitors from Libya Severus built a large and imposing structure to stand in front of this new wing, the Septizodium (SHA, Severus 19.5). Although it was entirely demolished in 1588–1589, it is known from 16th-century drawings (Figure 12.3).

These show a massive screen wall with a single niche in front of which stood a three-storey high screen of columns, which makes it look very much like a free-standing version of the scaenae frons of a Roman theatre. Two niches are shown in fragments 7a and b of the Marble Plan.1 Because the word ‘SEPTIZODIUM’ runs a long way beyond the two niches on the plan, it has been suggested that the Septizodium may originally have been longer, perhaps with seven niches, the outer ones semicircular and the middle one rectangular like the Septizodium at Lambaesis.2

A fountain spout belonging to the Septizodium, now in the Palatine Museum, may suggest it was a nymphaeum, which raises the possibility that the urban function of the Septizodium was similar to scenic monuments like the nymphaea at Miletus and Lepcis Magna.

Figure 12.3  Rome, engraving showing the Septizodium (E. Du Pérac, I vestigi dell’antichità di Roma … Rome 1575).

During the later second century ad there had been a growing awareness of the spiritual consolation to be found in eastern cults. Exotic religious practices were not in themselves unusual, as the numerous temples of Isis and Mithras at Ostia show, but official imperial patronage of such cults was rare at this time. Not surprisingly Eastern cults were promoted by Septimius Severus, who came from Lepcis Magna in North Africa and whose wife was the daughter of a Syrian priest of Baal.

A temple in Rome was dedicated by Septimius Severus to Serapis, who protected his two sons and whose image he adopted in his final portraits. It is sometimes identified as the gigantic and dramatically sited temple, measuring 56 × 84 metres, which occupied part of the Piazza del Quirinale. Including the vast monumental staircase, 21 metres high, which led up to it from the Campus Martius, it was the largest temple ever built in Rome.

Parts of it still survive in the gardens of Palazzo Colonna and the Pontifical Gregorian University. If the drawings of Palladio are correct the temple is the only one with 12 columns on its façade, each one of which was 21.17 metres high. The drawings also show Asiatic ornament of the kind found in late Hadrianic and early Antonine buildings.

In ad 211 Septimius Severus died in Eburacum (York) and was succeeded by his sons, Caracalla and Geta. In the following year Caracalla had his brother killed and his name removed from all monuments. In order to gain tax revenue he extended Roman citizenship to all freeborn inhabitants of the Empire, gave orders for a new bathing complex to be built and then embarked upon a series of campaigns with the aim of extending the Roman Empire eastward.

The Baths of Caracalla, built between ad 212 and 216, were at the time the largest in Rome and remained one of the three largest (Figure 12.4). They were situated in the

Figure 12.4  Rome, Baths of Caracalla (ad 212–216), bathing block: plan.

same southern part of the city favoured by his father, and accessible from a new road, the Via Nova, parallel to the Via Appia (SHA, Caracalla 9). Opposite was the Mutatorium Caesaris, the place where the horses and chariots used by the emperor were kept for his journeys within the city (wheeled vehicles were not allowed in Rome during daylight hours).

This part of Rome, beyond the Colosseum and called in the 17th century the disabitato (the uninhabited, elevated part of the city away from the Tiber) is still largely verdant. The massive gaunt walls of the baths are an impressive sight, unencumbered as they are by later structures. Set within a high enclosure, measuring 328 × 400 metres, which provided facilities such as a running track, gardens and libraries, is the main bathing block which measures 220 × 114 metres (138 metres including the projecting caldarium).

Unlike the earlier Baths of Trajan, the bathing block is entirely detached from the perimeter wall. Its rather austere NE wall is punctuated by eight doors and an occasional window, which give little indication of the ingenious spatial effects of the interior. However, a study of the ground plan reveals that the complex is a masterpiece of design clarity, in spite of its functional complexity. A key factor in the design is the intersection of the two major axes in the middle of the frigidarium.

The longer axis embraces the frigidarium and its adjoining exercise yards (palaestrae), while the shorter indicates the normal bathing sequence: caldarium (hot room), tepidarium (warm room), frigidarium (cold room) and natatio (swimming pool). The building is symmetrical around the short axis, so that all facilities were duplicated.

There are four sets of entrances on the NE side flanked by columns, the outer ones leading to a set of three rooms which give direct access to the palaestrae, and the inner ones leading to rooms at the sides of the nation, which give access to five rooms containing the apodyterium (changing rooms). The high NE wall was designed to shield the open-air swimming pool from the sun.

The interior side of the wall, facing the nation, was decorated with two storeys of colonettes which framed niches encrusted with marble and polychrome glass mosaic. The niches were divided into three groups of three by four giant order columns.

The glittering incrustations, mirrored in the sparkling water of the unroofed swimming pool, measuring 25 × 50 metres, must have been dazzling when glimpsed by the bathers entering from the frigidarium. The central room of the complex was the frigidarium, originally roofed with three cross-vaults buttressed on each side by three barrel vaults (Figure 12.5).

The cross-vaults, covered with polychrome glass mosaic, must have glowed in the light of the eight clerestory windows with the same exotic splendour as the mosaics of a Byzantine church. There were plunge baths under the four outer barrel vaults, while the middle ones offered a vista from the patio on one side through to the caldarium on the other. At the ends of the other axis were the palaestrae, onto which opened large semicircular exedras, once paved with the athletes’ mosaic now in the Vatican Museum.

The tepidarium was a small room with the dual function of transition and insulation between the cold rooms on one side and the hot rooms on the other. As such, it formed a suitably modest prelude to the enormous circular caldarium, a huge domed room, 35 metres wide, lit not by an oculus, as was the Pantheon, but by windows. Over half of the rotunda projected from the perimeter wall of the block to gain full advantage of the afternoon sun. There are seven hot plunge baths in the thickness of the drum, each heated by its own furnace.

Flanking the caldarium were hot rooms, probably both Laconica (dry heat) and sudatorium (sweating rooms) with vast windows facing SW to absorb as much of the sun’s heat as possible. Two of the rooms opening off the palaestrae were partially heated and may have been used for massage. Behind the hot rooms, staircases led up to terraces on the roof of the porticoes.

The baths were stripped of most of their furnishings over the years and columns found their way to Pisa cathedral and S. Maria in Trastevere during the 11th and 12th centuries.3 In

Figure 12.5  Rome, Baths of Caracalla, cold room (frigidarium), looking SE.

1545–1546 the excavations of the Farnese Pope Paul III uncovered some enormous pieces of sculpture, including the Farnese Bull, which stood in the middle of the SE palaestra; also the Farnese Hercules and the Latin Hercules, which stood between the columns on the SE side of the frigidarium, all now in the Naples Archaeological Museum. This rich decoration extended to every part of the baths. It has been calculated that there were 108 sculpture niches in the main bathing block.

Furthermore, the planners of this remarkable complex not only had to take into account the bathing facilities, but also services, water supply, drainage and heating. It has been estimated that to build the baths a workforce of 6,000 would have been required, working 300 days per year over a period of four years.4 The architect not only had to plan a labyrinth of rooms, each of which imposed its own functional and aesthetic demands but fitted them remarkably skilfully into an almost perfectly rectangular enclosure. The result is a masterpiece of planning and possibly the most successful of all the major Roman bath buildings.

Caracalla was murdered in ad 217 and in the brief reign of his successor, Macrinus, formerly Prefect of the Praetorian guard, the Colosseum was struck by lightning. This caused a fire which consumed the wooden seating of the summa cavea as well as the wooden flooring of the arena. The damage to the building was so great that it had to be closed for many years and the games transferred to the Circus Maximus.5 Macrinus was succeeded by Elagabalus, a 14-year-old cousin of Caracalla, who encouraged the worship of the sun-god, with whom he identified, and hence spread the oriental cult of the living sovereign.

He built a large temple of Sol Invictus (SHA, Elagabalus 3.4–5) in the area known as ‘Vigna Barberini’ where a succession of buildings have been found: a rich house of the Augustan period; Nero’s revolving dining room; and the Gardens of Adonis, which formed part of the Flavian Palace. The temple, measuring 40 × 60 metres, was peripteral with 8 × 12 columns and faced NW towards the Palatine. It was inside a collonaded enclosure, measuring 110 × 150 metres.

In it Elagabalus assembled many of the most sacred pagan relics in Rome, the aniconic statue of Cybele, the fire of Vesta, the Palladium and the shields of Mars, in a syncretistic attempt to assimilate all these aspects of paganism into the worship of the sun.

Elagabalus built himself a palace on the site of a large imperial property near St. Croce in Gerusalemme, complete with a circus, in which Elagabalus liked to drive his chariot (SHA, Elagabalus 6.3). It was originally c. 565 metres long × 125 metres wide, compared with c. 620 metres for the Circus Maximus and 520 metres for the Circus of Maxentius.

He also built the Amphitheatrum Castrense, a small amphitheatre, measuring only 88 × 75.80 metres and later incorporated into the Aurelianic wall. Its façade originally consisted of three storeys of openings framed by Corinthian half-columns and pilasters.

The western end of the circus, cut by the wall, was excavated in 1959 and it was found that the part of the circus outside the wall was 450 metres long. In the early fourth century ad the palace was the favourite residence of Constantine’s mother, St. Helena. Constantine turned a basilical hall into the church of S. Croce to house a fragment of the True Cross which Helena had brought from Jerusalem. The complex was known from the sixth-century ad as the Sessorian palace.

Several monuments are ascribed to his successor, Alexander Severus (ad 222–235), such as a monumental public fountain just outside the Esquiline gate, supplied by a branch of the Aqua Claudia or the Anio Novus. Although stripped of its marbles and sculpture, the brick-faced concrete ruins, 18 metres high, are still an impressive sight. The water entered at the back of the building, about 10 metres above the ground, and divided into five streams which flowed into an upper basin.

It then ran through further jets down to a semicircular basin where people could draw their water. The Baths of Nero, which also seem to have been rebuilt by Alexander (SHA Alex. Sev. 25, 3–4), are described as one of the most beautiful buildings in Rome (Philostratus, Apollo. 4.42). The murder of Alexander Severus in ad 235 brought to a close the last stable dynasty for the next 50 years of anarchy and civil war.

On several occasions, the Empire and even Italy itself were invaded. In this bleak period one building stands out, the baths on the Aventine built by the emperor Decius in his short reign of 22 months (ad 249–251). Measuring 44 × 70 metres, they were only one-eighth the size of the central block of the Baths of Caracalla, and their layout probably followed that of North African baths rather than the great imperial Thermae of Rome. Although designed as public baths, by the fourth century they seem to have been mainly used by the senatorial aristocracy whose villas filled the nearby area.

It is significant that by far the most substantial building project in the 40 years after the death of Alexander Severus was the construction of a 19-kilometre-long wall circuit for Rome, mostly built by Aurelian between ad 271–275. The very scale of the project and the fact that Rome now needed such protection must have added greatly to the sense of insecurity which began to make itself felt in the middle of the third-century ad.

The new wall, 7.8 metres high × 3.5 metres thick, enclosed an area of 1,400 hectares (3,500 acres), over three times as much as the fourth century bc ‘Servian Wall’ which enclosed only 426 hectares (1,065 acres). The line of the wall followed defensive features whenever possible and left large, indefensible buildings outside.

The number of earlier monuments incorporated into it, such as the Praetorian Camp, the Amphitheatrum Castrense, the Pyramid of Cestius (Figure 2.13), the Porta Praenestina (Figure 5.4), as well as stretches of aqueduct on both sides of it, are evidence that the wall was thrown up in haste. Built of brick-faced concrete capped with merlons, it had rectangular towers every 100 Roman feet (29.60 metres) projecting 3.5 metres and rising higher than the wall.

The most important roads, such as the Via Ostiensis and the Via Appia, originally had gates with two arched stone openings, with a gallery above to house the mechanism of the portcullis and the garrison, and were flanked by large semicircular towers which rose to the same height.

A well-preserved gate is the Porta Asinaria, close to St.John Lateran, from which issued the Via Asinaria which joined the Tuscolana (Figure 12.6). In the early fourth century ad Maxentius began digging a ditch outside the circuit. In ad 402–403 Arcadius and Honorius raised the towers and gates a storey and the height of the walls to 16 metres.

The two entrances through the gates were made into one by Belisarius (c. ad 530–540). The wall was repaired by Theodoric in the sixth century and in the ninth century and extended by Pope Leo IV to include the Vatican. Despite many subsequent alterations, the wall served as the city’s principal defence for 1,600 years and most of the circuit still stands.

Aurelian’s other large project, the Temple of the Sun, is known from drawings of Palladio to have had a rectangular forecourt with apsidal ends. The temple itself was circular and was placed in the middle of a rectangular precinct. This feature and the fact that the funds for its building came from Palmyra, following the defeat of Zenobia in ad 273, links it with eastern temples, such as the Temple of Bel at Palmyra (Figure 11.17). The monotheistic dedication also suggests the eastern influence.

The half-century of troubles came to an end, temporarily at least, when Diocletian was proclaimed emperor in ad 284 in Nicomedia, which he declared to be the eastern capital of the Roman Empire. He quickly associated himself with a co-emperor, Maximian, appointing in ad 293 two subordinates or Caesars, Constantius Chlorus and Galerius, as designated successors, an arrangement known as the Tetrarchy.

Each of the four was given control over a portion of the Empire, which necessitated the creation of new imperial capitals. The consequent decentralisation of power was a further indication of Rome’s diminished position within the Empire. Diocletian expended much of his building energy at Nicomedia, where he had built a palace and circus by ad 304 (Lactantius, de mort.per sec . 17.4–5).

It remained the most important city in the eastern Empire until the foundation of Constantinople in ad 324. Diocletian also spent time at Antioch whereby ad 303 he had built a palace alongside the large and important circus, which was c. 520 metres long, excluding the careers, and had a capacity of 80,000, making it one of the largest known.6


Figure 12.6  Rome, Aurelianic wall (ad 271–275), Porta Asinaria.
Figure 12.6  Rome, Aurelianic wall (ad 271–275), Porta Asinaria.

The buildings of Rome also required considerable attention following years of neglect and decay. In ad 283 a fire had swept the area between the Forum Julium and the Basilica Julia, with the result that much of Augustus’ work has been transmitted to us in brick-faced concrete.

The Basilica Julia was reconstructed by Diocletian as well as the Curia Julia whose austere brick-faced concrete façade can be seen today, relieved only by the large entrance doorway and the three windows higher up (Figure 3.6). The lower part was originally covered with marble veneer and the upper stuccoed. It was an extremely tall building, internally 21 metres high, 18 metres wide and 27 metres long, following approximately the proportions prescribed by Vitruvius.

The marble paving and wall decoration with statue niches framed by colonettes belong to the reconstruction. Recent studies have shown that there were no adjoining buildings, that it abutted directly onto the Forum Julium behind it and that there was a columnar portico in front of it.

In ad 303 Diocletian visited Rome to inaugurate a set of five pink Aswan granite columns erected upon the rostra to celebrate the tenth anniversary of the Tetrarchy. Four of the columns, 36 Roman feet (10.66 metres) high, bore statues of the tetrarchs and the fifth, 40 Roman feet high, a statue of Jupiter.

The base of one of them, the Decennalia base, carried relief sculptures, one of which shows the emperor being crowned by a victory as he pours a libation at a suovetaurilia (bull, ram and pig sacrifice). The sculpture has been described as ‘a pale, almost ghostly, reflection of the great achievements of Roman historical relief’.7

This was one of Diocletian’s projects which can be seen as harking back to the glory days of Rome. As too are a pair of bases in the Boboli Gardens of Florence, one of them showing a Victory in high relief with fussy classicising drapery, which may come from a triumphal arch erected by Diocletian (ad 294).

Diocletian’s greatest single project in Rome is the enormous bath building on Viminal hill which bears his name (Figure 12.7). Built of brick-faced concrete throughout, it seems to have been begun in ad 298 and completed in ad 305. Such a gigantic project implies a massive reorganisation of the brick industry. The outer enclosure, measuring 316 × 356 metres, was slightly smaller than that of the Baths of Caracalla, but its main bathing block, c. 144 × 244 metres, was considerably larger.

Unlike the Baths of Caracalla, it is in the heavily built-up centre of Rome with the result that many parts of the building have been incorporated into later structures. For example, the great curve of the outer circuit wall has transmitted its shape to the Piazza della Repubblica.

The octagonal hot room covered with an umbrella dome in the NW corner of the main bathing block was for a long time the Planetarium cinema, and the NW circular room in the outer circuit was turned into the church of St. Bernardo, making any attempt to trace the entire complex on foot a lengthy business. The layout of the main bathing block was similar to that of the Baths of Caracalla, with the two controlling axes intersecting each other in the middle of the frigidarium, and the block entirely detached from the perimeter wall.

Figure 12.7  Rome, Baths of Diocletian (ad 298–306), bathing block: plan.
Figure 12.7  Rome, Baths of Diocletian (ad 298–306), bathing block: plan.


But there the similarities end. First, the perimeter wall of the Baths of Diocletian was punctuated by a regular series of curved and rectangular exedras, giving it the appearance of a defensive wall akin to that of Diocletian’s palace at Split. This impression is confirmed by the severe rectilinearity of most of the rooms and their regular, even monotonous disposition, for example, the six rectangular rooms on each side of the frigidarium.

Instead of a great domed rotunda, one of the architectural triumphs of the Baths of Caracalla, the caldarium was a rectangular cross-vaulted room with four semicircular apses. However, the greatest splendor must have been the nation which measured c. 48 × 86 meters and covered over three times the area of that in the Baths of Caracalla.

At the sides were vaulted halls encrusted in polychrome mosaic, while high screen walls, decorated with a triple order of columns in the manner of the scaenae frons of a Roman theatre, shut the pool off from the surrounding enclosure and adjacent frigidarium. Michelangelo’s transformation of the tepidarium and part of the frigidarium into the church of St. Maria Degli Angeli means that some of the spatial effects of the interior can still be appreciated (Figure 12.8).

The Late Empire Part 2 | Roman Architecture | Second edition

The eight granite columns under the triple cross-vault stand in their original positions and the room is still lit by its eight lunette windows. It must be borne in mind however that the vaulting was originally encrusted in polychrome mosaic and that the interior would have had more the jewel-box character of a Ravennate church than the cool Mannerist appearance it has today.

In 1749 Vanvitelli was commissioned to enlarge the church and added a choir extending into part of the nation, thus transforming Michelangelo’s nave into a transept. The two architects thus exploited the two major axes of the baths, Michelangelo choosing the long axis and Vanvitelli the short. The 16th-century church and its 18th-century enlargement illustrate the dual axiality inherent in the fully developed imperial bath building.

Figure 12.8  Rome, Baths of Diocletian, cold room (frigidarium), looking NW.

The same rigid planning can be seen in the great palace Diocletian built for his retirement at Spalatum (Split) on the Croatian coast (Figure 12.9). More like a fortified camp than a palace, it reflected the uncertainties of the times and the need to enclose the comfortable Roman world within stout walls. Built between ad 300–306, it lay on the sea coast and was defended by a rectangular wall circuit measuring c. 180 × 216 metres.

At each corner was a square bastion with two further square bastions on each of the three landward sides. In the middle of each of these three sides was a gate, flanked by octagonal towers. On the seaward side, there was a landing stage and a single entrance to the palace at water level. Higher up, facing the sea, was a long colonnaded corridor where the emperor could stroll.

Two intersecting colonnaded streets divided the complex into four sections. The northern two sections were perhaps barracks, while almost half of the southern sections are taken up by the residential quarters. The route into the latter consists of three successive rooms: a ceremonial courtyard measuring 24 × 13.25 meters, whose sides are formed by 14 arches supported on 12 columns, 5.25 meters high with re-used marble Corinthian capitals.

A large octagonal mausoleum opens off the courtyard to the east, and to the west is a small temple whose barrel-vaulted ceiling is adorned with fine stone coffering. The end wall of the courtyard consists of an arcuated lintel within a pediment supported by four taller red granite columns; south of this is a circular domed vestibule; and finally, a suite of palatial rooms with a rectangular hall in the center, flanked by each side by six small rooms.

To the west is an lapsed basilical hall, perhaps a throne room, and what looks like a bathing suit. To the east is a large square room with three smaller square rooms opening off it, probably a triclinium (banqueting room). The actual rooms do not survive, but their layout can be clearly traced in the substructures below (Figure 12.10).

The shapes of the rooms and their arrangement have much of the regularity we have already seen in the Baths of Diocletian in Rome. The palace also has similarities with Romuliana, the palace of Galerius at Gamzigrad in northern Serbia, and the third/fourth-century ad Palatiolum at Melinda. Its outer fortifications echo those of the early fourth-century ad fortified villa at Mogorjelo in Bosnia Herzegovina.

Figure 12.9  Spalatum (Split, Croatia), Palace of Diocletian, ad 300–306: plan.
Figure 12.9  Spalatum (Split, Croatia), Palace of Diocletian, ad 300–306: plan.


In ad 286, because of its greater proximity to the dangerous Rhine/Danube frontier, Diocletian moved the capital of the western Roman Empire from Rome to Mediolanum (Milan), while he himself resided in Nicomedia. Milan remained the capital until ad 402 when it was besieged by the Visigoths and the court moved to Ravenna. Various Roman remains to survive, notably parts of the Roman wall circuit enlarged by the western emperor, Maximian.

The new circuit, built of brick, was about 4.5 kilometers long × 11 meters high and punctuated by eight gates and a number of towers, of which one, with 24 sides, survives to its full height of 16.60 meters. The cardo intersected the decumanus at the forum, west of which was the imperial palace, which seems to have been a very extensive complex covering a large area on the western side of the Roman city.

One excavated part consists of a large circular building, 20.70 meters in diameter, which may have been covered by a dome supported on a ring of columns and surrounded by a vaulted annular corridor. Preceding the circular building was a rectangular lobby with apses at each end and north of it a building with three apses and a hypocaust. To the west was a set of three rooms, the central one lapsed with perhaps a similar set of rooms opposite.

The SE arm of the decumanus, the road which led to Rome, was colonnaded for a distance of one Roman mile outside the walls. Near the NW branch of the decumanus, well outside the city walls, was the Mausoleum of Maximian. Near the palace was a circus, 470 meters long × 85 meters wide, partly incorporated into the defensive wall. One of its towers survives as the bell tower of S. Maurizio.

Also nearby was the theatre, a large building raised entirely on substructures and built in the mid to late first-century bc. An amphitheater has been partially excavated to the SW of the city and the large Baths of Hercules to the NE, including parts of a large frigidarium, 50 × 22 meters, with its apse set within the south side of a colonnaded palaestra.

Figure 12.10  Spalatum (Split, Croatia), Palace of Diocletian, substructures.
Figure 12.10  Spalatum (Split, Croatia), Palace of Diocletian, substructures.

The other Tetrarchs had their own capitals. Trier (Augusta Treverorum) in Germania Superior was the capital of Constantius Chlorus, whose empire included Spain, Gaul, and Britain. Trier was an old-established city on the banks of the Moselle which already possessed a number of imposing monuments, including the amphitheater and the St. Barbara Baths built in the later second-century ad. However, its greatest period of prosperity dates from the time it became Constantius’ capital.

His son, Constantine, resided there for a time and completed the palace and basilica begun by his father, as well as building the cathedral, the Imperial Baths, and probably the circus.8 He also built a number of warehouses in the harbor district and the famous Porta Nigra (Figure 12.11). For a hundred years Trier remained the most important city in the west apart from Rome itself. Many of these buildings have survived and taken their place among the most conspicuous architectural remains in the Roman provinces.

The basilica stood on the site of a smaller basilical hall which probably formed part of the residence of the regional procurator (Figure 12.12). It was a large hall with a double square ground plan measuring 100 × 200 Roman feet (29.6 × 59.2 meters) with an apse at one end. There were no internal columns and it had the widest nave of any Roman basilica.

The building was lit by two rows of round-headed windows that continued around the apse. The upper windows of the apse were just over a metre lower than the corresponding ones of the nave and were shorter. Also, the two central windows of the apse were narrower than the outer ones. These subtle optical devices give the impression that the apse is higher and wider than it in fact is.

These refinements and the unusual construction of the building, which was composed entirely of brick, not brick-faced concrete, are signs of the sophistication of Tetrarchic architecture. Externally the building had a strongly vertical accent because of the blind arcading framing the windows.

However, nails and impressions in the brick show that continuous wooden galleries originally ran beneath each row of windows, adding a compensating horizontality. There was a colonnaded courtyard each side of the basilica and the building itself had underfloor heating.

Externally it was stuccoed and the window frames were decorated by painted putti and vine scrolls in yellow on a red field. The rich interior was very much in contrast to its rather stark grandeur today. The floor was paved in black and white opus sectile and one of the niches contains traces of mosaic tesserae with blue and green scroll patterns on a gold ground.

It also formed part of a larger palace complex of which only a transverse narthex survives. Whether or not the basilica joined up with the complex found a little to the north, under the cathedral, must be resolved by excavation.

Figure 12.11  Augusta Treverorum (Trier, Germany), Porta Nigra, early fourth century ad.

Figure 12.12  Augusta Treverorum (Trier, Germany), basilica, early fourth century ad: reconstructed view of exterior (left), and plan (right). (After A. Boethius and J. B. Ward Perkins,

Etruscan and Roman Architecture [Harmondsworth: Penguin, 1970].)

The great Imperial Baths were among the largest outside Rome and raise the question of why they should have been built at all when Constantius had only recently finished rebuilding the equally large St. Barbara Baths. The answer may be that they were not for public use, but were connected with the imperial palace, which occupied a large portion of the eastern town. They were designed to occupy two city blocks, half as a gymnasium and half for bathing purposes (Figure 12.13). The main bathing block was much more compactly planned

Figure 12.13  Augusta Treverorum (Trier, Germany), Imperial Baths, early fourth-century ad: restored view (above), plan (below). (After A. Boethius and J. B. Ward Perkins, Etruscan and

Roman Architecture [Harmondsworth: Penguin, 1970].)

than that of the second-century ad St. Barbara Baths, and betrays the hand of a court architect, trained perhaps in north Africa to judge by the ground plan. In the event, it was never finished according to plan because of Constantine’s departure for the east in ad 316, and finally, the entire frigidarium area was scrapped.

The Porta Nigra was probably built by Constantine, but for whatever reason never finished, which explains its somewhat crude surface treatment (Figure 12.11). It owes its preservation to the fact that the hermit, St. Simeon, lived in it and later a church was erected over the gate incorporating most of the Roman structure. The two arched passageways had garrison rooms above and were flanked by two projecting semicircular towers.

It followed a well-established Roman type exemplified by the magnificent first-century ad Porta Palatina at Augusta Taurinorum (Turin) which had four arched passageways, two for traffic and two for pedestrians, and was flanked by imposing 16-sided towers. Other Augustan and early imperial gates were of a similar type, such as those at Augusta Praetoria (Aosta), Hispellum (Spello), and Augustodunum (Autun).

A feature of these gates is the separate entrance and exit, and the courtyard, where no doubt visitors to the town and their merchandise would be checked. The Trier gate, like the others, was designed to impress. Towers and guard rooms were decorated with rows of half-columns supporting continuous horizontal entablatures, but the effect is clumsy and the work bears signs of haste. Confirmation of this is the fact that inscriptions in the masonry show that the third story went up in three weeks.

Diocletian’s other Caesar, Galerius, who controlled the Danube provinces, made his capital at Sirmium in Diocletian’s province of Pannonia Secunda (northern Serbia). He also built a fortified palace at Gamzigrad in northern Serbia where he was later buried. Perhaps his greatest building achievement was the enormous palace at Thessalonica where he resided, much of which has been uncovered.

The city was already well-established by this date and lay on the strategically important via Egnatia which linked Asia and Italy. Galerius built his palace to the east of the old town. The palace proper and an adjoining circus lay to the south of the via Egnatia and his own mausoleum to the north. The via Egnatia was colonnaded at this point and another colonnaded street ran north to the mausoleum (Figure 12.14).

The intersection of the colonnaded streets was marked by a four-sided arch. The sides which faced the via Egnatia had three openings, a large one for traffic and two lesser ones for pedestrians. On the other two sides, there was a single opening. As the colonnades abutted against the arch it could not be decorated in the same way as a free-standing structure. This may partly explain the unusual nature of the reliefs, which consist of a series of long, rectangular panels, reminiscent of sarcophagus reliefs, set one on top of the other.

The mausoleum (Figure 12.15) is well-preserved mainly because it was converted into the church of St. George (c. ad 400). It is a domed rotunda with eight barrel-vaulted recesses in the thickness of the drum. Above each recess is a round-headed window, because, although the walls were massively thick, windows rather than an oculus had by then become the established method of lighting a domed room.

The structure of the vaults is of interest because pitched brick and mortar rubble is used, a technique that became common in Byzantine times. It also had a double curvature dome, which means that the lower part followed the normal curvature of a hemispherical dome, but, at a point 2.5 meters from the wall, changed to a steeper curvature, adding considerably to the stability of the structure.

The crown was a point of weakness in a dome, and it was the shallowness of the crown which caused the dome of Hagia Sophia to collapse barely 21 years after it was completed in ad 537.

At this point, mention should be made of the large Roman villa at Piazza Armerina in Sicily (Figure 12.16). Now dated to the period ad 310–320 it cannot have been built by Maximian as originally thought. It had a loose, rather rambling layout in contrast to the taut planning of Diocletian’s palace at Split. The polychrome mosaics in practically every

Figure 12.14  Thessalonica (Thessaloniki, Greece), Mausoleum of Galerius and monumental approach to it, including the Arch of Galerius across the main colonnaded street of the city, before ad 311: reconstruction. (After A. Boethius and J. B. Ward Perkins, Etruscan and Roman Architecture [Harmondsworth: Penguin, 1970].)

Figure 12.15  Thessalonica (Thessaloniki, Greece), Mausoleum of Galerius and the Arch of Galerius.


Figure 12.16  Piazza Armerina, Roman villa, ad 310–320: plan.

room, covering an area of nearly 0.4 hectares (an acre), link it stylistically with North Africa, but its layout is more reminiscent of Hadrian’s villa at Tivoli. Furthermore, in North Africa both villas and townhouses were of the single-story peristyle type. The main groupings of the entrance courtyard (2 on Figure 2.13), peristyle/audience hall (15 and 30), baths (8–12) and triclinium (46) were loosely related and on differing axes. Like other buildings of the period, the interior dictated the shape of the exterior.

The bathing suit, for example, was planned as a series of related interiors, resulting in a jumble of irregular spaces outside. Now that other villas of similar character, but seemingly smaller, have been found at Patti Marina and Caddeddi, both belonging to the fourth-century ad, the Villa at Piazza Armerina is no longer an isolated phenomenon.

When Diocletian went into voluntary retirement he compelled his fellow emperor, Maximian, to do the same (ad 305). Unfortunately, the orderly succession he planned did not materialise. A further round of civil war ensued, this time between Maximian’s son, Maxentius, and Constantine, the son of Constantius Chlorus. Maxentius held power in Italy for six troubled years and built prodigiously during that time.

He began work on a large imperial palace for himself on the Appian Way, which included a large circus and a mausoleum. The external length of the circus is 520 meters, less than the 620 meters of the Circus Maximus or the 565 meters of the Circus Varianus of Elagabalus, but it displays many of the refinements to be expected in a building of so late a date.

The starting gates (careers) were set out in a tight curve between two tall towers (oppida) built flush with the banks of seats on each side of the track. The dividing strip (spina) was short in relation to the arena as a whole and was angled, as was the seating between the meta Secunda and the careers, a sophisticated device to allow the spectators a closer view of the crucial start of the race.

The structure itself was of opus listatum with enormous numbers of amphorae incorporated into the fill of the vaults. His Mausoleum was a domed rotunda with a pedimental columnar porch in front, an arrangement that harks back to the Pantheon. It was set in the middle of a large columnar quadriporticus and was designed to be viewed on all sides.

The residential quarter, of great antiquity and only partially excavated, exhibits at least four main building phases. Situated on a low hill, its platform was supported by a late Republican cryptoporticus, 115 metres long, consisting of two parallel vaulted galleries.

A very capacious water cistern, 63 × 4.30 meters, was installed in the second-century ad, which fed a bath building and two nymphaea below the terrace. On the terrace various buildings can be seen, in particular a great basilical hall, measuring 33.10 × 19.45 meters, with terracotta heating tubes in the wall, installed when the original villa was turned into an imperial palace by Maxentius.

In ad 307 fire swept the area around Hadrian’s Temple of Venus and Rome, and although it left the outer colonnade undamaged, the twin cells had to be rebuilt by Maxentius. The new cells each terminate in an apse and were roofed with coffered barrel vaults supported on porphyry columns, a material much used in the Late Empire because its color had imperial connotations.

Maxentius also began building the adjacent Basilica Nova in ad 308, a colossal building with a broad nave, 25 × 80 × 35 meters high, covered by three cross-vaults buttressed at each side by three barrel vaults (Figure 12.17). The cross-vaults sprang at the level of the top of the barrel vaults and were given visual support by eight Corinthian columns of Proconnesian marble, the only surviving one of which was transported to the piazza in front of St. Maria Maggiore where it still stands.

The huge hall was well lit both by windows in the walls of the aisles and by a clerestory of eight lunettes under the cross-vaults. Both the lateral barrel vaults and the cross vaults were decorated with deeply sunken coffers, once elaborately colored and painted. The sheer bulk of the building is still impressive even after the collapse of one set of barrel vaults and all the high vaults. The basilica was an unorthodox building that broke the tradition of its great antecedents like the Basilica Paulli

Figure 12.17  Rome, Basilica of Maxentius (ad 306–312), looking NE.

and Basilica Ulpia, which were divided into nave and aisles by a double order of columns, had clerestory lighting and were covered by wooden roofs. The plan of the Basilica Nova is clearly derived from the frigidarium of one of the large imperial thermae, and as such, it had two major axes. In its original form, its main axis was to be the longitudinal one, and an apse was built at the far end opposite the entrance (Figure 12.18).

After the death of Maxentius the basilica was named after Constantine (Aurelius Victor, Caes. 40.26) who finished it, altering its orientation and inserting a new apse in its NE side. He also created a new entrance opposite, preceded by a porch of porphyry columns, in accordance with his policy of promoting buildings on the Via Sacra. A colossal statue of Constantine, parts of which are now in the courtyard of the Capitoline Museum in Rome, was placed in the original apse.

Another monument on the Via Sacra, immediately west of the Basilica Nova and probably of similar date, is a circular domed building, 50 Roman feet (14.8 meters) in diameter, with a concave façade flanked each side by wings, known as the ‘Temple of Romulus’ (Figure 3.2). It had a pair of porphyry columns framing the doorway, whose original bronze doors have been preserved. Pairs of cipollini columns framed each of the lapsed chambers which flanked the central rotunda.

The identification of this building has provoked many disputes. It used to be identified, on coin evidence, as a temple erected by Maxentius in honor of his young son, Romulus, who died and was deified in ad 307. A more recent suggestion is that it is the Temple of Jupiter Stator, flanked by shrines of the Penates, whose temple stood at the highest point of the Velia (Livy, 45.16.5).

If the original building had to be destroyed owing to the erection of the Basilica Nova, this was the nearest place to rebuild it. More mundanely the temple acted as a vestibule to the Temple of Peace and concealed its alignment, which

Figure 12.18  Rome, Basilica of Maxentius: reconstruction. (After H. Leacroft, The Buildings of

Ancient Rome [Leicester: W. R. Scott, 1969].)

differs from that of the Basilica Nova. The room of the Temple of Peace it gives access to now houses the church of Saints Cosmas and Damian built by Pope Felix IV (ad 527–530).

Constantine was proclaimed emperor by his troops at Eboracum (York) in ad 306 on his father’s death. This brought him into conflict with Maxentius whom he defeated in battles at Turin, Verona and near the Milvian bridge at Rome (ad 312). Constantine later built an arch over the Via Flaminia on the spot where he had marshaled his army for the battle. The Arch of Constantine near the Colosseum was built between ad 312-–315 and also commemorated his victory over Maxentius (Figure 2.11).

It was a triple arch similar to the Arch of Septimius Severus, although somewhat wider, measuring 25.9 × 7.4 × 21 meters high. Like the latter, it had three openings, a large central one flanked by two smaller ones, framed each side by four tall, free-standing columns supporting projecting entablatures. Its sculptural ornament was rich and varied, some of it Constantinian, but much of it removed from earlier buildings.

Over the lateral passageways were pairs of roundels of Hadrianic date showing hunting scenes set into a porphyry ground and below them narrative reliefs of Constantinian date. The attic was divided each side into three panels by four standing Dacian prisoners perhaps from the Forum of Trajan.

The central and largest panel contained the dedicatory inscription, and the lateral ones were filled with pairs of rectangular reliefs of Marcus Aurelius, whose features were replaced by those of Constantine. In the passageways and at the sides of the attic were sections of a magnificent frieze, showing a battle scene. The sculptures in the spandrels and on the column plinths were Constantinian and followed traditional themes.

The Baths of Constantine on the Quirinal (ad 320) are known from drawings by Palladio to have been of the imperial type with the usual succession of the caldarium, tepidarium, frigidarium, and natatio. The frigidarium was covered by three cross-vaults, the central one wider than the other two, with the usual four plunge baths in the corners.

Unusually, the frigidarium was prolonged at each end by two further rooms covered with three cross-vaults, each terminating in an apse and each almost as big as the main room. The caldarium has reverted to a circular plan like that of the Baths of Caracalla. Palladio’s plan shows a large curved wall south of the caldarium, with rows of seats.

The so-called ‘Temple of Minerva Medica’ (early fourth-century ad), in the gardens owned by the Licinian family, was a domed pavilion, 25 meters wide with ten sides; one was the entrance and the other nine had projecting semicircular apses (Figures 4.15 and 12.19).

The building is a good illustration of some of the building techniques used by late imperial architects. There were large windows in the drum and the envelope of the dome was comparatively thin. Lattice ribbing can be seen in the dome and 18th-century engravings show several of the ribs still standing independently of their filling. This led many to conclude that the ribs were designed to channel stresses in the same way as Gothic ribs.

However, the purpose of the ribs was probably to distribute load evenly within the dome. There were also amphorae in the dome above the windows, presumably to channel weight away from them. The ‘Temple of Minerva Medica’ may well have been built by Licinius who had been raised to the rank of Augustus by Galerius in ad 308.

After Galerius’ death in ad 311 and following the defeat and death of Maxentius in ad 312 Constantine met Licinius in Milan and the two promulgated the Edict of Milan, granting toleration to Christianity (ad 313). The edict was a masterstroke in a world that was increasingly seeking spiritual consolation and silenced Constantine’s most vocal critics.

In ad 324 Constantine inaugurated a new city to be called Constantinople on the site of Byzantium, an old Greek city on the European side of the Bosphorus, which stood at a critical geographic point between the Balkans and Asia Minor, close to both the Danube and Euphrates frontiers. It also stood at a major intersection of E/W trade. The site itself had many advantages. Roughly triangular in shape, it was surrounded on two sides by the sea,

Figure 12.19  Rome, ‘Temple of Minerva Medica,’ model in Museo della civiltà romana

and had a good harbor in the Golden Horn, whose mouth could be shut off by a chain. Like Rome, it had seven hills and there was plenty of room for expansion. In ad 330 Constantine made it the capital of the Roman Empire. This, more than any other action, spells the end of the old Roman Empire and the change to a new era. The final break the Classical tradition makes this an appropriate point to terminate the story of Roman architecture.





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