Work on the construction of a roundabout on the modern via Flaminia, in the locality of San Martino del Piano (Fossombrone, PU), exposed substantial remains of the ancient via Flaminia and of a small Roman bridge. The excavation area is situated at about 300 m east of the archaeological park of Forum Sempronii, on the edge of the Roman municipium founded in 130 B.C.

A stretch of about 30 m of the consular road was preserved here, lying almost exactly below the modern road, which follows its line, projecting out from it by about 1.5 m towards the north. As this was an extra-urban stretch of the road it did not present a basalt-paved surface but was a via glareata, characterised by a kerb of medium sized squared stones and a surface of cobbles and irregular stone chippings covered by a gravel layer (only preserved in a few places). A small bridge stood in correspondence with a torrent, which no longer exists but is visible on 18th century maps. It was constructed of large, squared blocks of local limestone with the aim of raising the road level in order to prevent possible swamping. The structure, in opus quadratum, is 2 m high and 4 m wide and its arch is now missing. The surface is paved with large, smoothed limestone blocks, mostly trapezoidal in shape and of irregular size, bedded without mortar, and presented a breakwater formed by two large oblique limestone slabs.

The materials found in association with the road date it to the late Republican period, between the 2nd and 1st century B.C., the period in which Forum Sempronii was founded. Based on the construction materials and technique the bridge dates to the Augustan period, probably between 30 and 20 B.C. This is not the only known infrastructure along the ancient via Flaminia in the Marche, where numerous bridges and substructures built using the same technique and datable to the same period are known. In fact, Augustus himself in his Res Gestae records the restoration of the consular road, including all but two of its bridges, in 27 B.C. Therefore, it is likely that the bridge at Forum Sempronii was part of the Augustan reconstruction and restoration of the via Flaminia.