While there are papal tombs in St. Peter’s Basilica, you can find many more underneath the church in the Vatican Grottoes. Situated below the modern basilica but above the level of the original 4th-century basilica, dozens of popes and members of royal families are entombed in the grottoes, spread out over a similar layout to the basilica above ground. The tomb of St. Peter himself is not in the Vatican Grottoes, but in the Scavi below them — accessible only via special guided tour.
You will find, however, the earliest pope buried in the grotto, 9th-century Pope Nicholas I, as well as the tombs of Queen Christina of Sweden, Emperor Otto II, and Queen Charlotte of Cyprus. There are also pretty, decorated chapels, such as the Chapel of St. Peter with its ornate gilded-arch ceiling, and artworks, including a 14th-century fresco of the Madonna by Pietro Cavallini.
Visit the grottoes, the Sistine Chapel, and St. Peter's Basilica on a complete tour of the Vatican, and consider booking a skip-the-line ticket to get ahead of the crowds.
Entrance to the Vatican grottoes is inside St. Peter's Basilica at the transept. The grottoes are open daily from 7am to 6pm during the months April through September, and from 7am to 5pm during the months October through May. Lines to get into the Vatican can get very long — book a skip-the-line tour with Viator for a seamless experience in the papal city.