Castel Sant'Angelo from the bridge

The Castel Sant'Angelo looms in the background as I stand on a bridge overlooking the Tiber River in Rome, Italy. The Mausoleum of Hadrian, usually known as the Castel Sant'Angelo, is a towering cylindrical building. It was initially commissioned by the Roman Emperor Hadrian as a mausoleum for himself and his family. The building was later used by the popes as a fortress and castle.