This bridge links the Tiber Island to Trastevere district. It was built around 46 BC probably by Lucius Cestius and left by Caesar to the government of Rome during the war with Spain. Numerous restorations and reconstructions were made during the centuries and its name has changed many times. 

In 365 it was restored by the Valentinian emperors, Valens and Gratianus, and therefore called “Gratianus’ bridge”; then, it was called “iron bridge” for the quantity of chains necessary to anchor the wheels that, together with a machine used to turn them, laid on boats linked together (this technique was necessary to grant a structure able to supply flour to the city of Rome when Vitigescut the aqueducts that supplied the mills on the Tiber in 537). 

In 1892, the bridge was partly rebuilt by adding the central arch with two big lateral arches, but after the 1900 flood they were shored up to reopen the ancient flow. It measures 85 meters x 8, the external part is in travertine, partly coming from the theatre of Marcellus, the inside is made of tuff. On the marble parapets, still existing, you can see the inscription concerning the restoration of 1892.