Nine caves filled with recently-discovered archaeological finds under the houses and the streets of the most ancient district of an old town.

A hidden tunnel of bones in one of Malta's oldest churches.

Jesus' footprints and the first catacombs in the world.

The largest catacomb system in the world.

Burial grounds for more than 1,000 bodies deep under the modern town of Rabat.

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.

The burial place of an obscure North African saint was turned into a macabre body preservation factory for the 17th-century Neapolitan elite.

The Neapolitan Cult of the Dead still cares for the skulls at this mini-Fontanelle.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

Charles Babbage's proto-computer, painstakingly brought to life.

Overshadowed by other, more famous Maltese catacombs, this ancient burial chamber has one of the best examples of a ritual agape table.

Thousands of well-dressed mummies below a monastery.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

This picturesque Umbrian city has a subterranean side that has long remained hidden.