Saint Peter's Basilica

The largest church in the world by interior, built between 1506 and 1626 over the supposed tomb of Saint Peter the Apostle, who was crucified upside down on this site under Nero. Holds Michelangelo's Pietà (carved when he was just 24), Bernini's vast bronze baldachin over the high altar, and the chair of Saint Peter sculpted in gilded bronze. The dome — designed by Michelangelo — was the model for every great dome that followed, from St. Paul's in London to the U.S. Capitol. Climb to the top for one of the city's best views. Free entry, but security and dress checks at the entrance can take 30+ minutes in peak season.