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!