Pons Aelius (Ponte Sant'Angelo), view from Ponte Vittorio Emanuele II, the next western Tiber brige in Rome

Todays Ponte Sant'Angelo is an ancient bridge in Rome, originally named Pons Aelius, "the Aelian Bridge" meaning the Bridge of Hadrian (Hadrian´s complete name was Publius Aelius Hadrianus).
Completed in 134 AD. by Roman Emperor Hadrian, to span the Tiber, from the city center to his newly constructed mausoleum, now the towering Castel Sant'Angelo. In the middle ages the original name went forgotten: after the ruin of the nearby bridge of Nero, pilgrims from the city were forced to use this bridge to reach St. Peter's Basilica on the othe bank, hence it was known also with the name of "bridge of Saint Peter" (pons Sancti Petri). In the sixth century, under Pope Gregory I, both the castle and the bridge took on the name Sant'Angelo, explained by a legend that an angel appeared on the roof of the castle to announce the end of the plague.
The bridge is faced with travertine marble and spans the Tiber with five arches, three of which are Roman; it was approached by means of ramp from the river. The bridge is now solely pedestrian, and provides a photogenic vista of the Castel Sant'Angelo.

more on https://en.wikipedia.org/wiki/Ponte_Sant'Angelo