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date: 15 July 2024

wall of Aurelianfree

wall of Aurelianfree

  • Rossana Mancini

Summary

In 271 ce, nominally in response to the empire’s state of vulnerability, the Emperor Aurelian decided to protect Rome with a curtain wall, a decision that may also have been driven by social pressures in the city and the form of which was motivated by economic limitations. Following its completion by Probus, the wall has subsequently received periodic improvements from Maxentius and Honorius through Theodoric and medieval and Renaissance popes and into the modern period when the walls became partially accessible to the public.

Subjects

  • Late Antiquity
  • Roman History and Historiography
  • Roman Material Culture

Updated in this version

Article rewritten and expanded to reflect current scholarship. Primary texts added and bibliography expanded.

The Construction of Rome’s Imperial Wall

Aurelian’s Plan

When Aurelian succeeded to the imperial throne, in 270 ce, northern European tribes posed a serious threat. The most pressing danger was posed by the Juthungi in Noricum, Rhaetia and northern Italy and by the Vandals and Iazygian Sarmatians along the Danube. In 271 ce the Juthungi penetrated as far as Umbria, though they were defeated at Ticinum (modern Pavia). It was in that very year that the Emperor Aurelian decided to protect Rome with a circuit of walls in an attempt to mitigate Rome’s state of vulnerability (see fortifications, Roman), an action mentioned by the emperor’s biographer in his Historia Augusta (Hist. Aug., Aurel., 21, 10) and which St. Jerome and Cassiodorus dated to 275 ce.1 Zosimus, writing in 412 ce (Zos. 1.49), added that Probus completed the project, while the Chronicle of John Malalas affirms that Aurelian personally supervised the building of the new defences.

Though nominally intended to provide security in the face of external enemies, it has also been suggested that the decision to launch a large-scale construction programme may have also been influenced by economic, political, and social considerations. During the first half of 271 ce there was widespread unrest in Rome. Tensions were revealed by a riot of the mint-workers while Aurelian was still busy stopping the Iuthungi. With the knowledge that he and his troops would shortly need to depart Rome again for a campaign against Zenobia, the self-proclaimed queen of Palmyra,2 Aurelian may have hoped that the construction of the walls would help to control the civilian population during his absence, demonstrating his commitment to the city and its defence and strengthening the authority of his regime.3

The choice of layout was guided by a combination of strategic concerns, economic considerations, and the need for speedy completion. Due to the strained relationship between the emperor and the Senate, Aurelian chose to build the wall on as much imperial land as possible, so as to avoid having to pay out large sums of public money to acquire further land, which would have required the Senate’s approval. As a result, no less than a third of the wall was built on imperially owned land, following a complex route that was also influenced by the densely populated urban nature of Rome. The wall cut across entire residential and commercial districts and incorporated a number of existing buildings, thereby saving time, money, materials, and labour.

The resulting defensive wall was approximately 19 km (12 mi.) long and encircled areas on both banks of the Tiber. It mainly ran along hill crests, with gates necessarily placed in the lowlands between hills, wherever it crossed the city’s main roads. Pre-existing funerary monuments located along these roads were incorporated into the towers flanking some city gates (Porta Salaria, Porta Nomentana, Porta Labicana-Prenestina), while elsewhere a wide variety of other buildings were incorporated including houses and boundary walls, as well as cisterns, porticoes, foundations, an amphitheatre, and a fortress. It was inevitable that aqueducts, which were vital to the city’s survival, would also end up incorporated into the walled perimeter where they entered the urban areas. The river was also employed as part of the city’s defences, forming a natural barrier in western sections of the wall, which were lower and thinner along the riverbank, while Hadrian’s Mausoleum was transformed into a fortress guarding the Pons Aelius. There were fourteen main gates in total, and many smaller postern gates were built to allow the city’s population to move more freely. The wall was approximately 20 Roman feet (5.24 meters; 5.73 yards) high, not counting the parapet and merlons, and 12 Roman feet wide (3.55 meters; 3.88 yards), with a core of opus caementicium mainly consisting of tuff caementa, and external cladding of kiln-fired bricks. Rectangular towers were located at intervals of approximately 100 Roman feet (29.6 meters; 32.4 yards).

Construction

The external facades were mainly constructed using second-hand bricks partly sourced from the buildings that were demolished to construct the walls.4 The building technique used is fairly regular in appearance and features the thick mortar joints typical of 3rd-century Roman walls. The bond between the structural core and the cladding was strengthened by courses of bipedales sunk further into the concrete core at the end of each phase of building, that moreover provided a flat, level surface on which the next phase could begin. Construction was carried out by teams of builders who were simultaneously working on portions of curtain wall that were between 15 and 20 Roman feet long. The practice of dividing large-scale projects into smaller sections was common at the time and derived from a military architectural approach. Experienced military architects were responsible for the overall design of the wall, but the construction is accurate enough that it is believed to be the work of civilian rather than military workers.5 The absence of signs of putlog holes in the towers or curtain walls would seem to indicate that they were built using double scaffolding of the type depicted in the painting discovered in the tomb of Trebius Justus. Individual sections of wall were carefully bound together, often using bricks from adjacent sections of wall meshed together in an interlocking, sawtooth profile, while some areas feature thin courses of brick used to compensate for any deviations in the horizontal coursing of the masonry work.

Characteristics of Aurelian’s Wall

Along the wall’s exterior, a projecting brick cornice marked the height of an open walkway that ran along the top of the wall, protected by a crenellated parapet and reached via stairways located inside the gate towers. Traces of the original crenellations were preserved in the facing of the wall when it was later raised in height. Each tower featured a rectangular chamber (a “fighting top”) level with the battlements, large enough to permit the effective use of defensive artillery and lit from windows placed on all four sides. The bottom storey of the towers regularly consisted of solid concrete. Differences in the terrain along various stretches of the circuit led to variations in this general structure, such as in the adjacent valley close to the Amphitheatrum Castrense where there is a double curtain with two superimposed galleries.

The types of gates used in the Aurelian Wall were based on Augustan models, found in Augusta Praetoria (modern Aosta), Fanum Fortunae (modern Fano), Hispellum (modern Spello), Augusta Taurinorum (modern Turin), Nemausus (modern Nîmes), and Augustodunum (modern Autun). This type of gate is flanked by two protruding towers protecting one or two arched entrances topped by an upper storey with windows from which guards could open and close the gate using ropes and pulleys. Rather than traditional doors, the gates were closed by portcullises, which closed by sliding down grooves carved into the door jambs.

The functional defects of the new walls are easily recognisable through the “corrections” that would soon be made by the builders of Honorius at the beginning of the 5th century. The walls were too low to ensure that they would not be climbed and windows on the first level of the towers provided insufficient protection to the internal chambers of the towers. Despite these issues, it was a very large and impressive work, and would have required many soldiers to operate effectively.

First Changes to the Walls

Approximately forty years after the wall was built, repairs proved necessary. These were undertaken by the Emperor Maxentius between 306 and 312 ce (Chronograph of 354), who probably also had a ditch excavated along the length of the wall at this time. Though originally thought to have increased the height of the walls, the weight of recent scholarship has tended to deny Maxentius this contribution to the circuit, highlighting the existence of an intervening masonry layer between the original and the additions, and hypothesizing that Maxentius might not have elected to leave the city to confront Constantine and his army at Saxa Rubra had the walls been improved to such an extent.6

Honorius was the first to undertake extensive improvements to the wall (Claudian, Panegyricus de Sexto Consulatu Honorii Augusti, vv. 529–53), which Claudian hints may have been motivated by fears of an attack from the Visigoths. Such work may therefore have occurred roughly between 401 and 403 ce. In addition to Claudian’s account, three inscriptions found on the Porta Tiburtina, Porta Praenestina, and Porta Portuensis gates attribute the restoration of the wall, gates, and towers, as well as the removal of vast quantities of rubble from the vicinity of the circuit, to the Roman People and Senate, following the advice of the military commander, Flavius Stilicho, during the urban prefecture of Flavius Macrobius Longinianus.

Honorius’s improvements involved increasing the height of the wall from 6 metres (6.5 yards) to approximately 11 metres (12 yards; not counting the parapet and merlons). This was achieved by adding a covered gallery over the existing open-air walkway atop Aurelian’s wall. The gallery featured a series of open arches facing the city, but was solid on the external side, pierced only by narrow vertical windows through which archers could shoot (embrasures). Along sections of the curtain wall whose interior facade was built directly against the ground, a thinner wall than the Aurelian one below was built on top instead of a gallery, in such a way that the difference in thickness between the walls created a lower walkway, while the top of the new wall provided battlements protected by a crenellated parapet.

The height of each tower was increased by an additional chamber reached via an internal stairway. Each of these featured arched windows, while the windows of the earlier room were narrowed into embrasures, increasing their security from the ground level. The new chambers were covered by vaulted ceilings. In most surviving cases, these are cloister vaults featuring eight sails resting on an octagonal base. Four squinches aid the transition from the tower’s square layout, and above each vault was a four-sided pitched roof. The new chambers added by Honorius led to an upper walkway that ran along the top of the new gallery. Where it approaches some of the towers, a small passage between the tower and the walkway led to necessaria, latrines used by the soldiers on guard that jutted out away from the city.

The gate towers were strengthened at their base and heightened to the point where they became the imposing buildings visible today. The Porta Pinciana, Salaria, Nomentana, Tiburtina, Praenestina-Labicana, Latina, Appia, and Ostiense gates were equipped with walled enclosures, that is small open courtyards that faced the city and provided sheltered areas designed to house the guard corps. Honorius’s masonry featured an opus caementicium core and cladding made using reclaimed brick similar to that in previous phases. Unlike the technique used at the time of Aurelian, however, the large square bricks (bipedales) that had been used to bind the external cladding to the inner core were not employed.

Restoration, Reconstruction, and Demolition Work

5th- to 7th-Century Restorations

An edict issued by Theodosius II and Valentinian III in 440 known as the De Pantapolis ad Urbem that appears in the Leges Novellae ad Theodosianum Pertinentes (Novellae Val. 3, 5) indicates a need to repair the city wall by this time. Though Isidore of Seville states that Theodoric, King of the Ostrogoths, attended (redintegravit) to the walls of the city (muri) after making Ravenna the capital of his Italian realm in 493, today it is difficult to pinpoint these improvements beyond the alterations to the Porta Appia identified by Richmond.7 During the Gothic War (535–553) as detailed by Procopius of Caesarea, the wall was besieged many times and the city alternately repaired by the occupying forces. Procopius witnessed two major repair programmes commissioned by Belisarius, in 536 and 547 respectively (Goth. I.14.21; III.24).

Later Historic Modifications

The city wall was repaired several times during the 8th and 9th centuries. Pope Sisinnius ordered that sufficient mortar be prepared to restore the walls, but his premature death in 708 brought this repair programme to an end before it had begun (Liber Pontificalis I, 388). Later, Pope Gregory II (715–731) and his successor Pope Gregory III (731–741) both commissioned restoration work, and the sweeping repairs undertaken by Pope Adrian I (772–795) were part of his plan to return Rome to a position of political power. After Muslim “Saracen” raiders successfully pillaged the area of St. Peters in 847, Pope Leo IV (847–855), enclosed the area with a circuit (the Leonine Wall), and reconstructed towers and gates of the Aurelian Wall equipping them with iron bars. These works made use of large blocks of tuff or peperino, purloined from existing buildings, and brick-faced concrete in second-hand bricks, arranged in undulating rows.

In the years immediately following an agreement between Pope Eugene III (1145–1153) and Rome’s city council (renovated with the Renovatio Senatus) in 1149, further restorations and maintenance were undertaken by the city itself in a wide range of easily recognizable materials: flint, tuff, peperino, travertine, fragments of marble and brick are all laid in a haphazard fashion, and included an inscription on the Porta Metronia of 1157.8

Following the return of the papal seat from Avignon to Rome in 1377, restorations began to be marked with papal coats of arms. Three towers between the Porta Ostiense and the Tiber, open at the rear and built using roughly squared blocks of stone alternating with rows of brick and cubilia (the pyramid-shaped stones of the opus reticulatum) purloined from ancient Roman buildings may thus be attributed to Pope Nicholas V (1447–1455).9

More dramatic changes were made necessary by the advent of firearms. From the mid-1400s on and throughout the 1500s, high, slender towers and vertical curtain-walls were gradually replaced with lower, stouter versions, evolving into sloping, bastioned facades better able to resist the impact of cannonballs, including eighteen new bastions planned by Pope Paul III’s (1534–1549) architect Antonio da Sangallo the Younger. Though this project was not completed, approximately 400 metres (437 yards) of wall between Porta Appia and Porta Ostiense were demolished at this time to build the Ardeatine Bastion.

The Janiculum Wall and the Destruction of the Aurelian Wall in Trastevere

In 1642 anew project, under Pope Urban VIII envisaged abandoning the ancient imperial curtain wall in preference for a new line of defences, but the only element completed was a bastioned curtain wall in the Trastevere district and along the slopes of Janiculum. As a result of these the Aurelian Wall along the right bank of the Tiber was demolished lest it fall into enemy hands during a siege and prove a threat. The remaining stretch of wall within the new circuit lost its purpose and inevitably fell into ruin.

The Wall in the 19th and 20th Centuries

Despite Giuseppe Valadier’s plan to restore the wall in 1806, this period saw extensive destruction of the wall. In 1838 Pope Gregory XVI (1831–1846) had Porta Labicana and Porta Praenestina demolished to make Porta Maggiore visible. The wall played an important role during the battles to defend Rome in 1870, when Honorius’s ancient embrasures were adapted for the use of rifles, but after Rome officially became the capitol of a unified Italy in 1871, the wall quickly lost its defensive purpose, becoming instead an impediment to the city’s development and progress. By 1896, there was talk of the need to demolish sections of wall in order to improve mobility in the city. Work to demolish the wall by Via Abruzzi began on 26 November, and was followed by similar action elsewhere, such that almost 70 metres (76 yards) of curtain wall were destroyed in just a few years. The Porta Salaria was demolished in 1921 in order to aid the flow of traffic even though Vespignani had reconstructed this ancient gate in 1873, repairing the damage left by cannonballs during the Capture of Rome in 1870. In December 1900, a decree transferred the ownership of the Aurelian Wall to Rome’s city council, triggering some restoration programmes along with continued demolition; the last alterations were carried out in 1951 when arched galleries were opened up to make way for a new road connecting the city to the coast (modern-day Via Cristoforo Colombo).

A number of projects have now made the walls partially accessible to the public. Since 1932, the Porta Pia has been the home of the Historical Museum of the Bersaglieri, and the Museum of the Via Ostiense, inside Porta Ostiense, was founded in 1950. In 1970, Rome’s city council opened Porta Appia to the public, as well as a long stretch of Honorius’s gallery towards Porta Ostiense, and created the Museo delle Mura (the Museum of the Walls of Rome) inside the Porta Appia.

Primary Texts

  • Aurelius Victor. Liber de Caesaribus, praecedunt Origo gentis Romanae et Liber de viris illustribus Urbis Romae, subsequitor Epitome de Caesaribus, ed. F. Pichlmayr. Leipzig, Germany: Teubner, 1961.
  • Cassiodorus, Senator. Magni Aurelii Cassiodori Senatoris opera. CCSL 118–123. Turnholt, Belgium: Brepols, 1958–1973.
  • Chronographus Anni CCCLIIII, ed. T. Mommsen. Monumenta Germaniae Historica, Auctores Antiquissimi 9.1. Berlin: Weidmann, 1892.
  • Claudian. Claudii Claudiani, Panegyricus de sexto consulatu Honorii Augusti, ed. Michael Dewar. Oxford: Oxford University Press, 1996.
  • Eutropius. Eutropi Breviarium ab urbe condita, ed. F. Ruehl. Leipzig, Germany: Teubner, 1887.
  • Historia Augusta, vol. 2, trans. David Magie. The Loeb Classical Library. Cambridge, MA and London: Harvard University Press, 1922–1932.
  • Isidore of Seville. Historia Gothorum, Wandalorum et Suevorum, ed. Theodor Mommsen. Monumenta Germaniae Historica, Auctores Antiquissimi 11.2. Berlin: Weidmann, 1893.
  • Leges Novellae ad Theodosianum Pertinentes, ed. Theodor Mommsen. Berlin: P.M. Meyer, 1905.
  • Liber Pontificalis. Le Liber Pontificalis. Texte, introduction et commentaire, ed. Louis Duchesne (with additions by Cyrille Voger). Paris: Ernest Thorin, 1955–1957.
  • Malalas, John. Ioannis Malalae Chronographia, ed. Johannes Thurn. Corpus Fontium Historiae Byzantinae 35. Berlin and New York: Walter de Gruyter, 2000.
  • Orosius. Historiarum adversus paganos, Libri VII, ed. A. Lippold and trans. A Bartalucci. Milan: Mondadori Valla, 2001.
  • Procopius Caesariensis. De Bello Gothico, ed. Wilhelm Dindorf. Corpus scriptorum historiae Byzantinae 2, Procopius, vol. II. Bonn, Germany: Weber, 1833.
  • Zosimus. Zosimi comitis et exadvocati fisci Historia nova, ed. L. Mendelssohn. Leipzig, Germany: Teubner, 1887.

Bibliography

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Notes