An underground burial site is known as a CATACOMB, which is an ancient form of burial consisting of a subterranean gallery with side chambers. Catacombs were used by the ancient Greeks and Romans, and later by early Christians, to bury their dead. They are typically found in areas of high population density, such as Rome, Paris, and Jerusalem. Catacombs are often associated with dark and mysterious places, and are sometimes used as a setting for horror films.