Quattro Capi ("four heads") refers to the two marble pillars of the two-faced Janus herms on the parapet, which were moved here from the nearby Church of St Gregory (Monte Savello) in the 14th century.

It was commissioned by Lucius Fabricius, the curator of the roads and a member of the gens Fabricia of Rome.

It is constructed from two wide arches spanning 80 feet, supported by a central pillar in the middle of the stream.

COERAVIT | IDEMQVE | PROBAVIT ("Lucius Fabricius, son of Gaius, superintendent of the roads, took care and likewise approved that it be built").

A later inscription, in smaller lettering, records that the bridge was restored under Pope Innocent XI, probably in 1679.