This network of conjoined cellars was riddled with traps and supposedly allowed the townspeople to pretend their homes were deserted.

Two monstrous faces loom over a village in Czechia.

A church of bones, decorated with 40,000 human skeletons.

A 400-year-old mummified arm dangles from the ceiling of St. James the Greater, serving as a warning to thieves.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

An old asylum graveyard that's been abandoned for half a century attracts those seeking a dark thrill.

A saintly relic hidden in a Prague church basement.

A collection of anatomical samples from one of the first anthropologists to suggest that humans reached North America by crossing the Bering Strait.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Two stunning 17th-century libraries and a cabinet of curiosities.

A morbid secret lies hidden within the beautiful walls of the Boston Athenaeum.

Books bound in human skin and H. P. Lovecraft's letters are among a few of the treasures this library has to offer.

One of the now-less-hidden floral gems of the "Emerald Necklace."

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Walk through Czech history in Prague's largest graveyard.

The medieval castle built as headquarters for the Pope's secretive Knights Templar.

Along the Palisades skyline are the ruins of a large mansion built in 1911 and demolished in the 1930s.

An Australian lake whose pink hue defies scientific explanation.

A reportedly haunted 14th-century church is curiously facing the “wrong direction.”

Ancient snack bar of the Roman Empire re-opened.

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

Ever hear of the Milazzo Cage?

The astonishing collection of an infamous criminologist.

David Sedaris called it "The greatest shop in the world."