Spello’s boundary wall is one of the most important legacies of the Roman period, allowing us to reconstruct the entire route that embraced the ancient historic centre. It extends for about 1.8 km from north to south and is elongated in shape. Unfortunately in the north-eastern part the wall is no longer identifiable, but between the south-eastern and western sides over half of it is still visible. The wall is built of small blocks of pink limestone from Mount Subasio that are rectangular in shape and arranged according to the opus vittatum technique; the inner core is instead made of opus coementicium and the gateways are built of large blocks of greyish limestone.
The boundary wall dates back to 30/20 BC. and was a benevolent intervention undertaken by the emperor Augustus, later restored in the late antique period. However, due to the monumentality and aesthetic quality of the work, it is very likely that the walls were built more to embellish the city and emphasize the age of Augustus than to defend it.
Along the stretch of wall there are still three ‘posterns’ or pedestrian crossings between the inside and the outside of the city, and five Roman gates: Porta Venere, Porta Urbica and Porta Consolare in the southern part, and Porta di Augusto and Porta dell’Arce near the Rocca (fortress). It is certainly one of the best-preserved fortified structures in Italy.