Castel Sant'Angelo is a historic fortress located in Rome, Italy. Originally built as a mausoleum for the Emperor Hadrian in the 2nd century AD, it has served various purposes over the centuries, including a papal residence and a military stronghold. The structure features a cylindrical design topped with a statue of the Archangel Michael, which gives the castle its name. Today, Castel Sant'Angelo is a museum that showcases art and artifacts from different periods of its history. Visitors can explore its impressive architecture, enjoy panoramic views of the Tiber River, and learn about its significance in Roman history.