These 17th-century mummies are no longer naturally preserved, but remain on display today.

Jesus' footprints and the first catacombs in the world.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

This small chapel is built of human bones and decorated with a golden skeleton.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

An ancient ossuary in Rouen.

5,000 skulls in memorial to those killed by the Khmer Rouge.

Artfully arranged bones of 5,800 Austrians.

The personal charnel house of Anton Bruckner.

Skeletons dressed in extravagant 18th century royal costumes cavort in the aisles of this German basilica.

Thousands of well-dressed mummies below a monastery.

Mysterious painted skulls in Moravia.

The remains of 40,000 humans, meticulously stacked in a tiny churchyard shed.

One of the largest ossuaries in Spain is packed from floor to ceiling with bones.

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

This German bone house contains the remains of some 20,000 souls.

A house of bones — but nobody is quite sure to whom they belong.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

In 1830, cemetery workers in Cham unearthed a chamber housing thousands of skeletal remains from the 13th century, which can still be viewed today.

This landmark church concealed a crypt packed with bones that was discovered thanks to the London Blitz.