Chemin de Chateauneuf, 04300 Mane, France
The bridge, 40 meters long and 3.2 meters wide, has three segmental arches with a span-to-rise ratio of up to 3:1. Its spans measure 2.80 meters, 7.90 meters, and 11.40 meters; the thickness of the two larger arch ribs ranges from one to two Roman feet, making the structure one of the few Roman bridges whose rib thickness-to-span ratio is below the commonly accepted ancient standard of 1:20.
The bridge was built from local limestone, the shape of which varies depending on its function: the arches consist of wedge-shaped slabs, while the spandrels are made of irregular stone masonry. The main pier is protected both upstream and downstream by large triangular cutwaters made of rectangular stone blocks. The paved road sharply rises from the left bank to the main arch, then descends more gently to the higher bank on the opposite side. The parapet, which was partially dismantled in 1993, was apparently repaired at the same time.
According to the Italian bridge engineer Gazzola, the Pont-sur-la-Laye dates from the late 1st or early 2nd century AD, thus belonging to roughly a dozen known Roman segmental arch bridges. However, there is an opinion that it is much younger and was built in the 11th century, with the two side arches and their cutwaters added only in the 17th century.
Sources:
https://en.wikipedia.org/wiki/Pont_sur_la_Laye
