Catacombs underground cemeteries. The word, meaning “by the hollows,” originally described the location of the burial place of Saint Sebastian, in Rome. In the ninth century it came to be applied to all underground vaults of the early Christians. The practice of using these vaults for burial was not exclusively Christian, however.

Catacombs have been found in various parts of the ancient Christian world. The most important and extensive are those built near Rome in the first to fourth centuries.

The Roman catacombs consist of a maze of passageways about three feet (90 cm) wide, often built on several levels connected by staircases. Niches, one above the other, are cut into the walls to serve as burial places. Martyrs and other important people were laid to rest in chambers off the main passageways. Some graves were decorated with pictures and Christian symbols. Later the walls were plastered and decorated with frescoes.

The catacombs were used as places of refuge during the persecutions of the Christians, because burial places were protected by law. In the third century, when this protection was withdrawn, the Christians closed the entrances and made secret ones.

Persecution stopped when Emperor Constantine recognized Christianity in 313. The catacombs continued to be used for burials until 410, when Alaric and his Goths sacked Rome. Then the vaults were closed to prevent them from being plundered. By the 10th century they were forgotten. In 1578, quite by accident, they were rediscovered, and the work of restoration was begun.

The most important of the catacombs is that of Calixtus (or Callistus), where third-century popes were buried. Near it, on the Appian Way, is the catacomb of Saint Sebastian, where Saint Peter and Saint Paul are said to have been buried for several months.