A UFO-shaped event building originally intended to be a science museum showcasing the future.

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

Hiding the longest subterranean river known in the world.

A maze of crosses marks the jumbled divide between the Netherlands and Belgium.

Incredible labyrinth of man made caves.

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

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

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

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

Three floors of musical instruments coming from all corners of the world and hundreds of years of musical history.

This Netherlands museum holds a gloriously mechanical collection of ornate musical automata.

The Bloemen Route, or “Flower Route”, stretches 25 miles through prime Dutch tulip country as a result of “tulip mania,” the world’s first economic bubble.

Oldest Museum of the Netherlands is a true cabinet of curiosities.

The giant scales in this museum can still tell if someone is one of the devil's brides just by weight.

A 'living museum' in Leiden, the oldest of its kind in the Netherlands.

A miniature city, once ruled by the Queen of the Netherlands.

The largest 19th century panorama in the world still in-situ.

A seven-century-old jail tells a not-so-pleasant history of crime and punishment.

Now a museum, this building was once a 14th-century monastery and the place where the founder of the Dutch nation lived and was assassinated.

Wind power station for making famous Ketel One vodka.

Birthplace of the "Cat in the Cradle" and a cluster of iconic, original windmills that let the Dutch tame the seas.

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

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