Monks turned this mountain into a temple by digging grottoes, tunnels, and a huge pagoda-like hall.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

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.

Europe's second largest ossuary wasn't discovered until 2001.

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.

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.

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

The mystery of the Putim Ossuary involves a tricorn hat.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Structure built from the skulls of vanquished foes.

Controversial site of what could be Europe's first pyramid.

An abandoned brutalist monument whose history has been lost to the ages.

This surreal memorial/cemetery is a necropolis of crumbling stonework and puzzle-shaped headstones.

A forgotten and crumbling Yugoslav monument to the victims of fascism.

This brutalist monument is inscribed with 9921 names of Yugoslav partisans who perished during WWII.

These warring psychedelic crags commemorate an unsuccessful military operation.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

This museum preserves the hand-dug tunnel that kept Sarajevo afloat during the Serbian siege.

This top-secret nuclear bunker hidden in a Bosnian mountain has been converted to a modern art exhibition space.