Castel St. Angelo

 Castel St. Angelo was originally Hadrian's Mausoleum, and was later at times a fortress, a prison, and some very fancy Papal apartments. There is a very cool passage from the Vatican to Castel St Angelo for the Pope to use in case he needs to flee to safety in the castle. The things that look like walls in the pictures below are this corridor, named Passetto di Borgo, and it is very cool. The castle is cool as well. Be sure to have a drink at the charming cafe on the top floor of Castel St. Angelo.