Explore a surprising lesser-known gem in the city center before jumping outside the city walls to the mazy Roman Catacombs. Go deep underground in a dark world of secret cults and ancient wall paintings with a small-group guided tour. Visit 2 contrasting underground sights with an expert guide. Discover the place of a hidden cult 14 meters below St. Clement’s Basilica and descend into the twisty tunnels of the Catacombs of Domitilla.