The Aurelian Walls were Rome’s second major circuit of defensive walls, built in the late third century CE under Emperor Aurelian. Unlike the earlier Servian Walls, which had enclosed only the central hills of the city, this new system protected a vastly larger urban area that reflected Rome’s growth over several centuries.
Aurelian came to power during the Crisis of the Third Century, a period of political fragmentation and military instability. During his reign, he defeated breakaway regimes such as the Gallic Empire and the Palmyrene Empire, restoring unity to Roman territory. But even as he secured the empire’s frontiers, Rome itself faced new threats. Germanic groups had invaded northern Italy in 270 CE, and unrest among mint workers in the capital followed in 271 CE. The city was no longer safe without serious fortification.
In response, Aurelian ordered the construction of a new defensive circuit around Rome. The project began in the early 270’s and took roughly five years to finish. It was one of the largest building efforts in Rome for generations, if not centuries.
The completed walls stretched for about 19 kilometers, enclosing an area of roughly 13.7 square kilometers. They were approximately 3.5 meters thick and 8 meters high, with towers placed at regular intervals of about 30 meters. Later emperors continued to modify and strengthen the system. Maxentius raised the parapets, while Honorius carried out major reconstructions in the early fifth century, significantly increasing the height and defensive capacity of the circuit. By late antiquity, the system had been expanded further and included hundreds of towers, thousands of battlements, and numerous gates and service structures.
The new walls reflected a changed understanding of Rome itself. Unlike the Servian circuit, which enclosed the traditional Seven Hills, the Aurelian Walls incorporated large new districts such as the Campus Martius, Trastevere, and areas to the north, east, and south of the older core. In doing so, they brought much of the city’s Augustan administrative structure within a single defensive boundary.
To reduce construction time and cost, the builders incorporated existing structures into the wall circuit. These included the Castrense Amphitheatre, the Pyramid of Cestius, the Castra Praetoria, and sections of the Aqua Claudia near the Porta Maggiore. Modern estimates suggest that roughly one-sixth of the circuit was made from pre-existing buildings.
Significant portions of the Aurelian Walls still survive today, along with several major gates, including the Porta Maggiore, Porta Tiburtina, Porta Ostiense, and Porta San Sebastiano. Other stretches remain visible across different parts of the city, including along the Corso d’Italia, between Porta San Giovanni and Porta Ardeatina, and along the Tiber near Porta Ostiense.
The walls remained an important defensive system throughout late antiquity and the medieval period. They helped protect Rome during raids in the ninth century, which later led to the construction of the Leonine Walls around the Vatican Hill, an area not included in the original circuit. The system remained militarily relevant until the nineteenth century, when Italian forces breached Porta Pia in 1870, marking the capture of Rome and the end of papal rule.
Today, visitors can explore sections of the walls and visit the Museo delle Mura at Porta San Sebastiano, which is dedicated to their history and construction. Operated by Musei in Comune di Roma, it offers models, diagrams, and interpretive material that help explain the scale and function of this vast defensive system.
Bibliography:
- Claridge, Amanda. Rome: An Oxford Archaeological Guide. 2nd ed. Oxford: Oxford University Press, 2010.
- Dey, Hendrik W. The Aurelian Wall and the Refashioning of Imperial Rome, AD 271–855. Cambridge: Cambridge University Press, 2011.
- Hillin, Matthew Conner Lee. Divide and Fortify: A Study of Roman Urban Fortifications in the Late Third and Early Fourth Centuries CE. Tucson: University of Arizona, 2023.
- Mancini, Rossana. “The Wall of Aurelian.” Oxford Research Encyclopedia of Classical Studies. Oxford University Press, 2015. https://doi.org/10.1093/acrefore/9780199381135.013.6871
- Platner, Samuel. (1929). “Muri Aureliani.” In A Topographical Dictionary of Ancient Rome (p.348‑350). Retrieved from: https://penelope.uchicago.edu/Thayer/E/Gazetteer/Places/Europe/Italy/Lazio/Roma/Rome/_Texts/PLATOP*/Muri_Aureliani.html
MURI AURELIANI, * the walls begun by Aurelian after the war against the Marcomanni and before that against Zenobia in 272 (Hist. Aug. Aurel. 21, 39; Aur. Victor. Caes. 35; Chron. 148; Eutrop. ix. 15; Oros. vii. 23; Hier. a. Abr. 2290) and finished by Probus (Zosim. i. 49).1
A restoration by Arcadius and Honorius in 403 is attested by the inscriptions on the portae Portuensis, Praenestina, and Tiburtina (CIL vi. 1188-90 2 ) and by Claudian (de sexto cons. Hon. 529); and the description of the walls (DMH) appended to the Einsiedeln Itinerary is generally attributed to this period (Jord. ii. 155-178, 578-580; DAP 2. ix. 424). Repairs by Theodoric are attested by brick stamps (CIL xv. 1665 b, 27; cf. PAS i. 52-55), as well as by Cassiodorus (Var. ii. 34; Chron. Min. ii. 160 (500 A.D.); cf. ib. i. 324. 67; ii. 283. 14, if ‘ moenia ‘ refers only to the city walls.
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One-third of the whole circuit and all the gates are said to have been destroyed when the city was stormed by Totila, but this is an exaggeration (Procop. BG iii. 22, 24); it was restored by Belisarius.3 Of the Popes, Hadrian I and Leo IV (the latter adding the Civitas Leonina) were especially active in repairing the walls (LPD i. 518, n. 48; ii. 137, 138); the Roman senate repaired them in 1157 (v. PORTA METROVIA), and much was done by the Renaissance popes, as their arms show. The greater part of the circuit remains, except along the river from near the porta Flaminia to the pons Aurelius on the left bank, and from the porta Aurelia to the porta Portuensis on the right bank. The former disappeared in the Middle Ages (ASRSP 1879, 79-121; 137-171), and the latter under Urban VIII, who brought the new porta Portese about 500 metres nearer the city (for the towers on the river-bank, see Roma iii. (1925), 317), and connected it and the porta Aurelia (S. Pancrazio) by a new line of fortifications with the Leonine city, which had been re-fortified by Paul III and Pius IV.
Otherwise, the line of the walls has remained unaltered since the time of Aurelian, except for the construction of a great bastion by Antonio da Sangallo the younger for Paul III (see PORTA ARDEATINA), in pursuance of a scheme which was not continued; and comparatively few openings for traffic have been made, despite the growth of the modern city. The line selected was the octroi boundary of the time of Commodus, which was marked by cippi (CIL vi. 1016a-c, 8594, 31227; BC 1892, 93 sqq.; LR 71, 72; Mitt. 1897, 150-156; cf. infra, fig. 2). Existing buildings were incorporated in this, and subsequently in the wall, for about one-sixth of the total length (such as the supporting walls of the horti Aciliorum and horti Sallustiani, the castra Praetoria, the arches of the various aqueducts, from porta Tiburtina to porta Maior, and the Amphitheatrum Castrense). For the haste with which the work was done, see BC 1892, 104-106; LR 70-71.
Though the various restorations of which evidence may be seen in the walls themselves have not yet been brought into relation with the scanty historical evidence we possess, it is clear that originally the wall was not more than 25 feet high, and that it has since been heightened and the arcades added (see Richmond in Discovery vi. (1925), 293-295, and in BC 1927, 41-67).
The walls as they now stand form one of the finest products of the science of Roman fortification. They are built of concrete faced with brick, are about 12 feet thick, and of varying height, the ground level inside being generally considerably above that outside. 13 feet from the ground inside they are traversed by a sentinel’s passage passing through both curtain and towers, the latter occurring every 100 feet; they are quadrangular, project about 10 feet from the curtain, and rise about 20 feet above the wall (Ill. 33). The gates have double or single archways, according to their importance, with flanking towers, and only some of them have vantage courts. The material used for the walls was largely older brick (BC 1892, 91-93; PAS i. 1-86).
See Nibby and Gell, Mura di Roma (Rome 1820) ; Jord. i. I. 340-392; BC 1892, 87-111; Richter 66-72; LR 68-87; RE v. 1375. A valuable description of the walls made by Nicolas Audebert in 1576 (Brit. Mus. MS. Lansdowne 720) is published in Rev. Arch. 3. vi. (1885, ii.), 27-41); vii. (1886, i.), 124-138; 224-242; 336-340; viii. (1886, ii.), 3-39; 319-335; ix. (1887, i.), 54-58. See also the articles on the individual gates.
1 See also Ioh. Malal. Chron. xii. p. 299, Dindorf. ἤρξατο τὰ τείχη ῾Ρώμηςκτίζειν γενναῖα. ἦν γὰρ τῷ χρόνῳ φθάρεντα. αὐτὸς δὲ ἐφέστηκε τῷἔργῳ, καὶ ἠνάγκαζε τὸσυνέργεια ῾Ρώμης ὑπουργεῖν τῷ κτίσματι(repeated in Chron. Pasch. i. 229; cf. also Chron. Min. ii. 148).
2 The meaning of the phrase egestis immensis ruderibus is not very clear, and the level of these and other gates does not seem to have been raised as much as was hitherto believed (BC 1917, 193-217).
3 Chron. Min. ii. 108 (547 A.D.). He also had restored the walls before the siege by Vitiges (Procop. BG i. 14).
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