This Belgian theme park began as a refuge for bored church children and was closed down when a boy lost an arm.

These crumbling Nazi artillery bunkers are now fair game for massive graffiti projects.

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.

An industrial relic is now one of Europe's most staggering art spaces.

This unique Renaissance castle was turned into a home for Nazi occultism.

The Bauhaus-style former industrial complex is considered the world's most beautiful coal mine.

The abandoned mine where American troops discovered a treasure trove of art and artifacts hidden by the Nazis.

One of the only spherical 19th century gas containers left today.

Germany has its very own Centralia, whose spark remains attributed to "spontaneous combustion."

Visit the ancient, mysterious Roman catacombs ... in the Netherlands.

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

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

The last bastion of Roman presence north of the Alps looms over a German town.

A sandstone block marks the alleged spot where the legendary writer was conceived.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

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

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 striking fort on the Maginot Line looks just as it did after being destroyed in the Fall of France.

Once the local rulers had gone these enchanting ruins housed common folk in an almost real life fairy tale.

The somewhat misnamed 'Garden of Shells' lovingly built from found objects.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

The tallest tower in Cáceres's Old Town.