At the base of its pillars, the splendid medieval bridge over the Ambra englobes the remains of a bridge from the Roman age. A typical case of the medieval custom of reutilising an ancient construction, the bridge of Bucine rises on a side lane of the ancient Via Cassia which from Rome led to Florence. The original structure was most likely formed by at least five arches. Of these the pilae [the pilasters] on which the road surface rested, survive and still today testify to a particular architectural technique widely used in the imperial age to build vaults and domes. It was common practise to cast cement in wooden crates lined with squared blocks, as in this case.

Also quite interesting, however, is the medieval bridge which literally rests on its surviving pillars. Like a construction typology widely attested to also in Tuscany, the structure has the typical donkey-back profile, with the central arch of a greater span.