Castel Sant’Angelo is a historic fortress located on the banks of the Tiber River in Rome, Italy. Originally built as a mausoleum for Emperor Hadrian in 139 AD, it later served as a castle, prison, and papal residence. Connected to St. Peter’s Basilica by a fortified corridor, it played a key role in the defense of the Vatican. Today, it is a museum offering panoramic views of Rome and exhibits on its rich history spanning nearly two millennia.