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

This Prague museum collects brutalist relics and memories from the country's former Soviet rule.

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.

Countless grotesque faces stare out from this eerie Prague art wall.

A Jenga-style cylindrical tower of books that appears to go on forever.

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

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

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

This nearly invisible wire transforms much of the city into one big, symbolic home on the holy day.

Deep under Manhattan is the largest construction project in city history. So far, the project has taken the lives of 23 workers, or "a man a mile."

A room in New York City that contains 250 cubic yards of dirt worth a million dollars.

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

This lower Manhattan bar is set up in an old bank vault that rests beneath a skyscraper that hides even more historic splendor.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

Bored potato-guarding Nazis etched their thoughts onto a brick storage building in Copenhagen's Meatpacking District.

Six beautiful wooden giants are hidden around Copenhagen.

A hip bar decorated with walls of golden skulls.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

This unique Renaissance castle was turned into a home for Nazi occultism.