A floating cat sanctuary on an Amsterdam canal.

A curious collection dedicated to human and animal anatomy and pathology.

A unique seaside cave where Aleister Crowley faked his own death.

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

Jesus' footprints and the first catacombs in the world.

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

Artfully arranged bones of 5,800 Austrians.

The personal charnel house of Anton Bruckner.

Mysterious painted skulls in Moravia.

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

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

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

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

A 1,000-year-old church holds the bones of the Christian martyrs who died hiding inside it.

The mystery of the Putim Ossuary involves a tricorn hat.

In a small churchyard in Dingolfing, Germany the quaint Schusterkapelle is there to remind you of your imminent mortality.

Structure built from the skulls of vanquished foes.

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

Among the oldest structures in Madrid, these Moorish walls once guarded the medieval city of Mayrit.

The largest prehistoric cemetery on the Balearic Islands dates back over 2,500 years.

This embalmed man is one of the best preserved mummies from the Canary Islands.

A small church ornamented with medieval erotic sculptures.

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

A display of torture devices used in the Spanish Inquisition and other scourges of medieval Europe.