This cave system allegedly holds the "metallic library" of a lost ancient civilization.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

One of the famous Czech artist's lesser-known Prague installations appears to be a glowing fetus affixed to a drainpipe.

The ruins of this medieval castle on a foggy hill tell the story of a once-mighty empire.

"We gonna rock down to Electric Avenue, and then we'll take it higher..."

This amazingly well-preserved villa just outside Pompeii boasts rare examples of ancient Roman paintings.

Lyon's "Wall of the Silk Weavers" is one of the largest murals in Europe.

This 15th-century Serbian Orthodox monastery also contained a school for illuminating manuscripts.

These mysterious Viking chess pieces spent centuries hidden on a remote Scottish island.

An abandoned railroad tunnel is now filled with bioluminescent bugs.

A university observatory dome painted to resemble the beloved 'Star Wars' droid.

Some call this eerie forest of crooked trees the "Bermuda Triangle of Romania."

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

This 17th-century pub once had a hole in its wall so the neighboring blacksmith could easily access beer.

Tokyo’s only Vaudeville-cuckoo clock–steampunk-Victorian curio cabinet time piece.

The oldest tavern in Lowell has dedicated fans of its fan.

This replica Viking village was created for a film that was never shot and is now open to visitors.

This terrifying glass bridge on the side of a mountain cracks as you step on it.

It celebrates a very stinky task and salutes London's fatberg-vanquishing team.

Modern commuters still pass through this 2,000-year-old Roman archway.

This modern New Zealand attraction honors ancient forms of astronomy and scientific understanding.

The forgotten remnants of a land-to-sea cable car that was once unique in the world.

Architectureal fantasy quarter of Rome.

A fairy tale castle in modern Rome.