Aurelian Walls

Rome had gone centuries without defences of its own. The city had spread far beyond the older Servian Wall, which enclosed only the seven hills, and its people took a certain pride in a capital that needed no fortification, held safe by the stability of the Pax Romana and by the army in the field. The sack of Athens by the Heruli in 267 unsettled that assumption. An invasion of northern Italy in 270 inflicted a severe defeat on the Romans at Placentia, modern Piacenza, and although the invaders were driven back it settled the argument. The historian Aurelius Victor states plainly that Aurelian's wall was meant to relieve the city's vulnerability; it may also have been meant as a signal that the emperor held power firmly and trusted the people of Rome to stay loyal. In the summer of 271 trouble broke out in Rome itself, when the mint workers rose in rebellion and several thousand died in the fighting.

Building is thought to have begun that same year and to have been finished within a few years, although Aurelian died before the end of it and the final work was carried out under Probus, towards 279. The job was left to the citizens themselves, because Aurelian could not spare a single legionary from an army worn down by civil war, famine and the Plague of Cyprian. Speed governed the design: separate gangs worked at once on different stretches, and buildings already standing were swallowed into the circuit of nearly 19 kilometres, among them the Amphitheatrum Castrense, the Pyramid of Cestius and part of the Castra Praetoria. As much as a sixth of the walls is reckoned to have been made of existing structures. No garrison could have held such a line, since the Praetorian Guard, the urban cohorts and the vigiles came to only about 25,000 men, but the wall was never meant to withstand a siege: raiders of the period struck fast at soft targets rather than settling down before a city, and a high wall with strong gates deterred them.

Maxentius reinforced the circuit between 306 and 312, raising parts of it and improving the watch towers. The deeper change came a century later, with Alaric's Goths in the peninsula, the army thinner and artillery scarce. It is credited to Honorius, and more exactly to his magister militum Stilicho: in about two years around 403 the height was very nearly doubled, the towers gained a second storey and many gates were rebuilt. The Mausoleum of Hadrian, across the Tiber, was drawn into the defences at the same time, bringing in the Vatican hill that Aurelian had been obliged to leave outside. Clearing a century of debris from the outer face exposed the wall to its full height and in places laid the foundations bare, leaving the structure dangerously unstable.

No enemy besieged the walls before 408, and none besieged the city in 410 either. On 24 August 410 Alaric came into Rome through the Porta Salaria, left improbably open; eight centuries after the Gauls in 390 BC, he was the first enemy to violate the soil of the city. Procopius of Caesarea reckoned about a third of the perimeter damaged by the start of the sixth century, and repairs used rubble from what the Goths had destroyed across the city. An edict of Theodosius II and Valentinian III in 440 ordered the urgent restoration of walls, towers and gates and appears to have been ignored; the earthquake of 443 made matters worse. In 455 the Vandals of Genseric entered as Alaric had, through open gates, the Ostiense and the Portuense, at a moment when civil authority in the city was practically non-existent and military authority absent with it.

The walls were finally restored at the end of the fifth century by Theodoric, the Ostrogothic king of Italy, after he had rid himself of Odoacer, the Herulian king of Italy, in a war that had itself damaged them. In 537 Vitiges, king of the Ostrogoths, attacked them repeatedly and in vain; the defence was conducted by Belisarius, general of the emperor Justinian, through the long siege of 536 to 538 that Procopius recorded, and forty years later came a Lombard siege reckoned at twenty years. The circuit still did the work it was built for: when Arab raiders came against Rome in 846 the walls stopped them, and the pillaging was confined to what lay outside the line, above all the basilicas of Old St Peter's and St Paul's-Outside-the-Walls. That exposure prompted the Leonine walls, built between 848 and 852 under Pope Leo IV to enclose the Vatican hill.

The popes came back to the walls repeatedly across the medieval and early modern centuries; a tower still carries an inscription recording a restoration of 1157, and Pius IX made further substantial repairs. The most conspicuous addition is the bastion near the Porta Ardeatina, some 300 metres of it, built in the first half of the sixteenth century by Antonio da Sangallo the Younger for Paul III, to shore up a sector that seemed too weak and too exposed to the Turkish threat; it was built to take cannon, where the old wall had been built to hold ballistae, and the cost of that single stretch seems to have persuaded the pope to suspend the work. Pius IV strengthened the walls in the second half of the century for fear of the Barbary corsairs then devastating the coastal towns of Lazio, adding a wider circuit in place of the Leonine walls. Gates were reworked for the city's traffic, the Porta San Giovanni opening in 1574 in place of the neighbouring Porta Asinaria. Urban VIII destroyed the walls round the Janiculum outright towards the middle of the seventeenth century. In 1821 the non-Catholic cemetery was opened hard against the walls beside the Pyramid of Cestius.

The walls kept a defensive role for centuries, alongside the Leonine and Janiculan extensions on the right bank, until 20 September 1870, when the Bersaglieri of the Kingdom of Italy opened a breach beside the Porta Pia, took Rome and ended the temporal power of the papacy. Built to hold off catapults and rams, the wall withstood five hours of bombardment; on one of the towers facing via Po an Italian army cannonball is still lodged in the brickwork.

That long working life is the reason so much survives: the walls remained Rome's principal fortification into the nineteenth century and fixed the limit of the built-up city until then. Preservation is uneven all the same. About twenty metres came down on via di Porta Ardeatina at Easter 2001, put down to rainwater infiltration and to maintenance the city had not carried out, although in 1999 it had spent a little under 30 billion lire on restoration; that breach was repaired in 2006, and a further stretch collapsed along viale Pretoriano in San Lorenzo on 1 November 2007 after days of heavy rain. A city resolution of 1980 provided for restoration and against unauthorised building, but houses, workshops, banks and military quarters are still built against the wall or have taken stretches of it inside their own property. The walls are protected as Italian national heritage, and the Museo delle Mura, inside the Porta San Sebastiano, is given over to them and to how the defences worked.