Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

Part modern art project, part traditional chapel, this see-through church is only substantial from the right angle.

Tour the sci-fi-esque reality of governmental disease management.

Historic psychiatric asylum and most-filmed location in the Great White North.

The eccentric mansion of one of the most popular horror authors of modern times.

Skeletons dressed in extravagant 18th century royal costumes cavort in the aisles of this German basilica.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

Rent out a glass igloo to watch the Northern Lights like you live in the future.

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

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

Climb right into the heart of this colorful Iceland volcano.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

Remnants of a Victorian garden feature sitting in public woodland.

Natural time capsule containing an alien ecosystem.

Moonbows over Kentucky.

Nine Gardens in one—with tea service.

This elegant arc of a waterfall marks a religious turning point.

Australian Lake set aglow by Noctiluca Scintillans.

This Irish show cave is said to have been the site of a Viking massacre that claimed 1,000 lives.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

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

The bizarre visions of H.R. Giger, tucked away in a Swiss medieval city.

This odd Chilean waterfall-cano hotel must be entered via a rope bridge.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.