An existential riddle in the world's largest ancient castle.

The elaborate clockwork contraptions in this Scottish gallery create small worlds of whimsy and horror.

A island reachable by a causeway at low tide is possibly one of the earliest Western European locations to be identified in text.

The Egyptian-inspired last resting place of Lord Kilmorey.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

No one knows who created the statues or if they are arranged properly—let alone the artwork's real name.

In Twickenham sits a small whitewashed castle that inspired Mary Shelley's 'Frankenstein.'

Street artists transformed an abandoned air vent into the beloved Star Wars robot.

This neolithic stone grave has been altered and restored so often its now more neo than lithic.

The remains of centuries of copper mining appear like an alien landscape.

High Victorian fantasy created a fairytale castle out of a ruined fortress in Wales.

Microscopic scenes; some call it novelty, some call it art.

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

Buried five stories underground, this Soviet bunker is packed with gas masks and Cold War paraphernalia.

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

A steampunk-styled three-floor factory churning out art, activism, and electronic beats.

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.

Dedicated to the unsung history of human waste.

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

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

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

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