The Mausoleum of Hadrian, usually known as the Castel Sant'Angelo, is a towering cylindrical building in Rome. 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, and is now a museum. It offers lovely views over Rome, the Tiber and the Vatican, and there is a pleasant cafe on one of the upper levels.