The Aurelian Walls
The Aurelian Walls were constructed between 270 and 275 AD at the behest of the Emperor Aurelian, as a defence for the city from the threatened invasion of barbarians from the North of Europe. The new enclosing wall had a perimeter of about 19 km and was constructed of sections of wall about 6.5m in hieght, with a parapet walkway along the top, punctuated every thirty metres by higher towers, covered by terraces.
Along the wall where the various roads left the city were also situated gates, whose form and size was determined by the relative importance of the roads.
After the first restoration works in the IVth century under Maxentius, carried out only in a few places where they were greatly needed, at the beginning of the next century, during the reign of the emperor Honorius, the entire circuit of the walls was modified with radical structural interventions which doubled their height. Thus two walkways were created in the walls, one a covered gallery with arrow slits for archers, and above that a second, which was open, although provided with battlements for the placement of war machinery. In the towers a second operations room was added, covered by a sloping roof and communicating with the lower room by means of a masonry staircase.
The ancient sources attest restorations carried out during the course of the VIth century under Theodoric, King of the Ostrogoths, and by Belisarius, the general of the emperor Justinian. In the following centuries restoration works were conducted at the behest of various Popes who, from the Xvth century, left memorials of their work through the coats of arms and inscriptions located directly on the walls.