The Catacombs of San Gennaro are underground paleo-Christian burial and worship sites in Naples, Italy, carved out of tuff, a porous stone.

The lower level is the oldest, going back to the 3rd-4th century and may actually be the site of an earlier pre-Christian cemetery later ceded to the new sect.

[2] As the burial areas grew around the remains of Gennaro so did underground places of worship for the growing Christian faith.

[5] The types of tombs include loculi, arcosoli, pits dug in the ground, and less often, sarcophagi made of tuff, or recycled marble and stone from older graves.

[2] The loculi are aligned vertically and the most simple style of burial found in the catacombs but not indicative of the status of the deceased.

Arcosoli, made for family funeral areas, are built into the walls of the galleries and cubicles and are more sophisticated than the loculi.