Built on the site where the apostle Peter was martyred, this is the largest Christian church in the world. Bearing witness to the history of Christianity from its earliest days, the basilica has been decorated over the centuries by some of the greatest artists of the Renaissance and Baroque periods and includes masterpieces such Bernini's canopy and Michelangelo's dome and beautiful Pietà. The treasury can be admired in the Museo Storico e Tesoro.