This is the only bridge that was built over the Tiber from the fall of the Roman Empire to the 19th century. Sixtus IV, when a cardinal, expressed a desire to have a new river crossing built, because the only way for him to reach St. Peter's from where he was living was to use the bridge at the Castel Sant'Angelo, a long and difficult road in those days.

When he was elected Pope, he commissioned the architect, Baccio Pontelli, to build the new bridge, authorizing him to remove the material needed from the Colosseum. Pontelli took what remained of the bridge that Agrippa had built from Campus Martius to Trastevere in the 1st century BC and incorporated it into his new bridge. The Ponte Sisto was inaugurated in the Holy Year of 1475.
During the 19th century, a heavy cast-iron superstructure was added; however, it has recently been removed, leaving the bridge in all its magnificent 15th century elegance. Just like the ancient Roman engineers, Pontelli included a circular eye in the central pier to help floodwaters flow through the bridge.
This became a kind of harbinger of the Tiber's dangerous floods, a problem that was solved only with the construction of new river banks, though to the detriment of the city's romantic setting.