The Walls of Ravenna
Ancient Ravenna lay much closer to the coast than it does today, the sea now having receded approximately six miles. Our earliest description of the site comes from Strabo (Geogr. V, I, 7):
“The largest city in the marshes is Ravenna, a city built entirely of wood and coursed by rivers. Bridges and ferries provide the only thoroughfares and when there is a high tide the city receives no small portion of the sea, relieving the city of filth and foul airs.”
The city was impervious to navies at sea thanks, Prokopios noted, to “shoals for no less than thirty stades” (BG, V, I, 16-18). With much the same protection on land due to “swamps” (Iordanes, Getica, XXIX). Its natural anchorage was used by numerous fleets in the republican period and led to Augustus stationing the fleet that policed the eastern Med in the area, giving rise to the port of Classis (mod. Classe–classis = fleet) two miles south-east of Ravenna. Rich palace complexes from this era probably belong to the Prefect of the Fleet or the head of the province (caput provinciae) of Flaminia et Umbria/Flaninia et Picenum.
Ravenna did not become a city of primary importance, however, until tragedy struck in AD 401 and the forces of Alaric forced Honorius to flee Milan. The city possessed good roads not only to western outposts but also passage to the East too (both for the military and grain supply). When Rome was sacked nine years later, Ravenna became the de facto imperial capital; a place that can be framed as either the west’s last redoubt looking east or the east’s window on the west.
This new status played no small part in the expansion of the town from a modest 33 hectares to a large city of 166 under Eastern Roman administration in the sixth century (with much of the eastern half of the city given over to the government as regio Caesarum), creating a circuit wall roughly three miles in length in the process. This development was particularly unusual considering the majority of its north Italian neighbours had become the “half-rotted corpses” bishop Ambrose complained about (Ep. 39, 3).
How its walls changed over this period is an interesting question. Once a colony, a modest oppidum of 485 X 865 metres in the south-west corner of the present city, it nevertheless boasted a monumental gateway in the form of the Porta Aurea, erected by Claudius in AD 43. Consisting of two arches flanked by two 8m towers, the latter were sadly destroyed by Venetians in the fifteenth century, with its gate following the same fate in 1582. Today the best preserved portions are near the Venetian angle-tower, the Torre dei Preti.
Later circuits were built by Valentinian III according to the ninth-century abbot and deacon Andreas Agnellus who composed the Liber Pontificalis ecclesiae Ravennatis (though archaeological evidence points to an earlier date). He relates that the emperor:
“… istius muri civitatis multum adauxit. Cingebatur autem (antea) quasi una ex opidis, et quod priscis temporibus angustiosa erat, idem augustus ingens fecit.”
A chronicle known as the Spicilegium ravennatis historiae claims an enlargement of the fortifications can be attributed to the Herul leader Odoacer:
“et coepit amplificare muros civitatis Ravennae a turre secunda alveo aquae ducto usque ad locum, ubi dicitur Arcoras septum super fluvium Padennae suis expensis, et laboribus propriis. Secondo autem cum cuncta gente aequissimum explevit murum civitatis… mediaque casta delevit a Ponte Apollinaris quousque ad Monetam auream, quam ex latere fecit, et fecit Palatium super flumen Padennae, ibique moratus est.”
While ninth-century sources refer to the eastern half of the city’s walls as “murus novus” without attributing the works to a person or period. Texts aside, however, it’s clear from archaeological reports (the curtain wall stands nowhere to its full height) that the wall’s height was 9m (and 2.2m thick). A relatively normal figure for peacetime Roman fortification (the Aurelianic Roman circuit was 7.8m, Barcelona was 9.19m, Verona was 11.8m) but is low in comparison with the fifth-century walls of Rome or the Theodosian circuit of Constantinople.
Towers were a rare feature. While gate-towers occurred at the Porta Aurea and Porta Salustra and the two surviving Venetian towers (Torre Zancana and Torre dei Preti) probably replaced earlier circular originals, it’s hard to speculate the location of any others given two waterways (Montone and Ronco) were forced to flow around the city in the fourteenth century, altering defensive requirements in the process. It’s not even a given that the principal city gates (Porta Teguriense, Porta Gaza and Porta S. Lorenzo) necessarily had towers either given absence of them at Porta Vandalaria.
A large number of posterns (30) and gates (14) studded the walls. In fact, the sheer number of them suggests several linked neither roads or paths but served as drains and/or secret passages. Sidonius Apollinaris described Ravenna as being “encircled by branches of the Po, which “flow into the town, bringing commerce in their wake [and often failed to flush out sewage that instead stuck itself to bargemen’s poles!]” so it’s likely that just as many streams entered the city as roads. Indeed, perhaps it was because there were so many waterways girdling the city that there were so few towers – they may have felt a little superfluous from a defensive standpoint.
For further reading see D. M. Deliyannis, Ravenna in Late Antiquity (2014)
 Despite the city’s relative prosperity, Ravenna was not included among those cities which were fortified by Gallienus or Aurelian in the wake of the Alemannic invasions of N. Italy in the second half of the third century. Other centres that had entirely new circuits added in the period were Bologna, Parma, Mantua, Brescia and probably Pisa.
 Even the larger total, however, made it a relatively small city when compared to other regional cities such as Trier (285 ha), Lyon (200 ha), Carthage (321 ha) and Milan (250 ha) in E. Cirelli, “Ravenna: Rise of a Late Antique Capital,” Debating Urbanism: Within and Beyond Walls AD 300-700 (2010), p. 243.
 “Taken altogether, the archaeological evidence suggests that Ravenna’s walls were not built by Valentinian and that the city was fortified shortly before or after AD 402” (D. M. Deliyannis, Late Antique Ravenna , p.54).
 Ravenna’s fortifications offer a half-way point between the lagoonal settlements like Torcello and Comacchio to the north (which relied not on wall but on nature and naval units for their defence) and towns that were approachable by the mainland such as Grado (which were equipped with strong circuit walls).
 Similar to the Porta Palatina in Turin and Porta Praetoria at Como, both of which are Augustan in date.
 See note 2.
 Rerum Italicarum Scriptores, I, (Mediolani 1725), 574-4; cf. Mazzotti 1970a, 289-90. The Spicilegium is a compilation of notices dating to 1346 or soon after: cf. M. Pierpaoli, Stori di Ravenna (Ravenna, 1986), 242-7.
 Sidonius, Epist. I, v. to Heronius.