Planned as the world’s first zero-carbon city, it had lofty ideals—but is only 5 percent completed and aiming for 50 percent carbon-neutral.

An archaeological site believed to be the burial place of the "mother of us all."

An ancient capital city that dates back 3,000 years old and harbors many surprises.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

A beautiful maze marks where three countries meet.

Peek through a transparent pyramid and drink in the mountain made of books.

The world's only museum devoted to the wonders of fluorescence.

A quirky bookstore hidden beneath a sea of whitewashed Greek villas.

Cretean quarry suggests real-life site for ancient Greek myth of the man-eating Minotaur in his labyrinth.

A spectacular cave and a beguiling lake.

The hallucinogenic center of the ancient world.

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

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

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

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

Gargoyle head that brings good luck.

An ethereal glowing blue ocean cave in Croatia.

This historic black and white monastery is one of Bulgaria's architectural jewels.

A medieval bridge stretches over a sulfur-rich river that leads to year-round natural hot springs.

The topiary maze at the Habsburg hunting lodge.

Op-art architecture designed for happiness.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

An alchemist's "magic door" stands in the middle of a Roman park.