A Cold War command center is hidden under an idyllic countryside.

Ancient man-made caves underneath small town Belgium.

This abandoned Belgian fortress is purposefully being left to nature.

Hiding the longest subterranean river known in the world.

Medical history with an amazing, if frighting, collection of wax diseases on display.

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

Science meets wall art to highlight the beauty of famous mathematical equations.

The bridges portrayed on EU currency aren't fictional anymore.

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

The largest flower auction house in the world.

A luxury hotel housed in a former 15th century Gothic church.

A bizarre form of natural mummification was discovered in the church of this Frisian village.

Strange secondhand shop showcasing taxidermy and oddies

Tucked away in the Leiden city hall are a group of works by famed artist MC Escher.

The tallest waterfall in the Netherlands is a lovely, stepped feature that is only 50 feet tall.

This historical Netherlands fortress still bears the marks of its single siege.

Two gravestones clasp hands over the religious divide.

The world's first interactive human body museum also serves as a chair for a giant orange man.

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

This beautifully designed star-shaped fort was the premier defense system of the late 1500s.

Colorful and chaotic stacked hotel in North Holland.

A beautiful maze marks where three countries meet.

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

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