This Luxembourg cave is covered in cryptic looking marks left by mining activity.

This tri-part waterfall is a little bit of fairytale beauty in the heart of Luxembourg's Little Switzerland.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

The ruins of this Dutch castle sit atop a labyrinth of once-secret tunnels and passageways, dating back over 900 years.

A beautiful maze marks where three countries meet.

The highest point in Belgium is a staircase to nowhere.

Hiding the longest subterranean river known in the world.

Sculpture designed by Turkish artist and professor Mehmet Ali Uysal.

A marble Lucifer hides behind the pulpit of this Gothic cathedral.

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

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

Ancient man-made caves underneath small town Belgium.

This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

When you're a great Russian Tsar, even your vomit gets a statue.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

Lavish royal estate punctuated with heated greenhouses.

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

A Portuguese Jewish cemetery filled with stunning grave monuments that date back to 1614.

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

Amsterdam's Red Light District leaves little to the imagination.

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

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

Community owned and operated, this property is home to a diverse set of nudists.