Elaborate series of tunnels where traces of mass suicide are still visible.

An Austrian house of bones filled with hundreds of intricately painted skulls.

Underneath this small church are 15,000 bones, arranged by an obsessive academic.

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

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

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

The mystery of the Putim Ossuary involves a tricorn hat.

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

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