Visit romes famous 3 tiered underground church the basilica of san clemente on a 15 hour guided tour taking in the churchs 1st 4th and 12th century buildings the tour showcases mosaics frescoes an underground schoolroom and a maze of corridors made from volcanic stone as you explore youll learn about the saints and cardinals connected with the fascinating church from your guide numbers are limited to 13 for a small group experience