Nighttime view from Ponte Principe Amedeo, crossing the Tiber River, in northeastern direction. The Ponte Vittorio Emanuele appears in the foreground of the photo. The initial purpose of Castel Sant'Angelo in the background, once the tallest building of Rome, was to serve as the mausoleum for the emperor Hadrian and his family. Their remains, and those of other emperors buried there, got lost. Later on, the structure was used as a fortress, prison, and residence.