This is a section of the beautiful Ponte Sant'Angelo in Rome spanning the Tiber River.
Emperor Hadrian had this bridge built in 134 AD to give access from the city center to his grand mausoleum. The ten Bernini-designed angels lining the bridge were added much later, in the 17th century (unfortunately I did not cross over to get close ups of them, but images can easily be found online).
About Hadrian's tomb, from Wikipedia:
The tomb of the Roman emperor Hadrian, also called Hadrian's mole, was erected on the right bank of the Tiber, between 135 AD and 139 AD. Originally the mausoleum was a decorated cylinder, with a garden top and golden quadriga. Hadrian's ashes were placed here a year after his death in Baiae in 138 AD, together with those of his wife Sabina, and his first adopted son, Lucius Aelius, who also died in 138 AD. Following this, the remains of succeeding emperors were also placed here, the last recorded deposition being Caracalla in 217 AD. The urns containing these ashes were probably placed in what is now known as the Treasury room deep within the building.
More about Castel Sant'Angelo from Wikipedia:
Legend holds that the Archangel Michael appeared atop the mausoleum, sheathing his sword as a sign of the end of the plague of 590, thus lending the castle its present name.
Today the building is a museum.