Along the Roman road to Gaul, not far from the Augustus Arch, we find a remarkable example of a Roman bridge dating back to the Augustan era to which the suburb of Ponte di Pietra (French for “Stone bridge”) owes its name. The structure of the bridge consists of a single lowered arch with a diameter of about 17 metres, made of radial quoins that are founded directly on very wide bases, reinforced by piers and built with large blocks of conglomerate rock. Originally the bridge was built on the waters of the Buthier torrent, but during the Middle Ages, probably after a flood, the river opened a new channel to the West – the current one – while the oldest one was reduced to a small canal that dried up completely with time. The bridge was partially buried under a layer of debris, then it was progressively filled in and it was fully brought to light in the course of the works carried out in the middle of the last century.