St. Paul (Rome), marble sarcophagus and fragments from the ancient Roman graveyard at the monastery´s cloister

The Basilica of St. Paul outside the Walls was founded by the Roman Emperor Constantine I over the burial place of St. Paul, outside Aurelian´s city walls.
As the Basilica founded on an ancient Roman graveyard and extensively modified and reconstructed during the centuries, many marble sarcophagi, fragments and inscriptions had been found in the ground. These are a small part visible now at the walls of the cloister (from Latin claustrum, "enclosure", a covered walk, open gallery, or open arcade) of the monastery of San Paolo fuori le mura. The cloister was erected there between 1220 and 1241.

more on https://en.wikipedia.org/wiki/Basilica_of_Saint_Paul_Outside_the_Walls