The catacombs were underground tombs near Rome where the early Christians were buried. These tombs were cut in soft rock in a sacred area surrounding the city of Rome.

When Emperor Nero began his persecutions of the Christians, they gathered in the tombs to worship. This was because every citizen was safe from attack in the burial grounds. Later, in the middle of the third century, even the burial grounds were not safe. The Christians then blocked up the regular entrances and made secret ones. They extended for miles in the underground galleries. It is said that the catacombs would be longer than the peninsula of Italy if the passages were in a straight line!

When the persecutions of the Christians ended under Constantine, the catacombs were visited by many pilgrims. When the Goths conquered and sacked Rome in A.D. 410, the entrances of the catacombs were filled up in order to protect them. By the twelfth century, the existence of the catacombs was forgotten. They were so well hidden that it was not until 1578 that one was accidentally found.

Passages in the catacombs are usually straight and from 3 to 4 meters deep. They were dug just wide enough for two grave diggers, one behind another, to pass along them with a bier. The stairs that led down were often 12 meters underground. At the bottom, galleries branch off in all directions.

Some of the catacombs have two or more levels. One, the catacomb of St.Sebastian, has four. The walls of the galleries were cut into Aches for the bodies of the dead. Originally, they were walled up with tiles or stone. Many of these partitions have given way, and present-day vectors to the tombs must walk between long rows of skeletons.