According to literary sources, in the mid-6th century BC, the sixth king of Rome, Servius Tullius, built a defensive wall surrounding a city that was very large for the time, enclosing all the hills and taking advantage of the natural slope.
Currently, the most widely accepted hypothesis is that a single fortification already existed in the Archaic period, and that the sections of wall made of grey granular tuff blocks (= Palatine tuff, commonly referred to as “cappellaccio”) could be attributed to this. These are considerably smaller in size than the large square blocks of yellow tuff on the Via Tiberina (= tuff of Grotta Oscura) that characterize most of the remains preserved today. In fact, these belong to the new city walls built at the beginning of the 4th century BC, in the aftermath of the disastrous invasion of Rome by the Gauls, as recorded by Livy in 378 BC.
The walls were then completely rebuilt in saxo quadrato, using large blocks of tuff from Via Tiberina, whose quarries were located in the territory under the control of the Veii; their massive exploitation, such as that which was to bring tens of thousands of blocks to Rome – via the Tiber – for the construction of the walls, could only be conceivable after the conquest of Veii in 396 BC.
The reconstructed perimeter of more than 10 kilometres marks out an area stretching from the river Tiber towards the north-east and the hills, running along the edge of them to exploit their height for defensive purposes. In the section of the Esquiline plateau, from Porta Collina to Porta Esquilina, where the walls ran along level ground rather than the edge of a slope, a wide moat in front of the walls and an embankment behind it artificially replaced the hillside.
The best preserved section is certainly the one next to Termini station, more than 10 metres high, while on the Aventine, on Largo Albania, is another wide section. This continues on Via dei Deci with the distinguishing feature of an arch, also made of tuff, probably the entrance to a chamber used to launch shots from the ballistae.
On the Esquiline, on the other hand, in the garden of Piazza Manfredo Fanti, where the Casa dell’Architettura [House of Architecture] is today, a large semi-circular structure, inside the line of the walls, suggests the presence of a probable manoeuvring chamber. The characteristic chiselled quarry marks are still visible on the blocks composing it.
2. Reconstruction of the wall circuit and archaeological evidence of the Middle Republican age, with indication of the sections examined (elaboration by Roma medio repubblicana 2020)(elaborazione da Roma medio repubblicana 2020)
3. Walls on Largo Albania, exterior side
4. Walls in Piazza Manfredo Fanti, interior side with semicircular structure