Walk through a well-preserved World War II Nazi prison and transit camp.

No shoes allowed on this trail, which is designed to be experienced barefoot.

This former Nazi castle was built as a school to train what would have been the future of the Third Reich.

What was once a bustling mining installation is now a bustling hub of contemporary art.

A beautiful maze marks where three countries meet.

Descend into the tunnels to experience the life of a coal miner.

Take a leisurely walk through the park to find the seven giant troll sculptures hidden throughout the park.

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

Climb inside an iron crystal magnified 165 billion times its normal size.

It has an American Dream Car exhibit, Europe's largest Formula One collection, and many, many mannequins.

This historic funicular system combines the old with the new while offering delightful views over the surrounding valley.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.

The castle was reconstructed to fit Kaiser Wilhelm II's romanticized vision of the Middle Ages.

One of England's most famous churches hides a pair of little known architectural treasures.

These giant yellow bowling pins seem to be defying gravity.

Rotterdammers' dirty minds gave this Santa a dirty nickname and cursed it to a life of wandering.

These slanted cubic abodes are a creative if odd solution to a zoning pickle.

Rejoice at Amsterdam's ‘pop temple,’ a former church reborn as a raucous music venue.

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

A Belgian self-built tower inspired by the Bible and ancient civilizations.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

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

A defensive structure built during the Hundred Years War has remained useful in one way or another for nearly 700 years.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.