It's forbidden to dig within this ancient Roman fort hidden beneath a playground.

A striking memorial to the Jews of Leiden who were murdered during World War II is scattered throughout the city.

A massive stone fox oversees a Rotterdam elementary school crosswalk.

Building Men of War and Indiamen from Holland's Golden Age.

Some 80,000 Delft Blue tiles line the inside of this Amsterdam walkway.

Made of 41,900 pieces of mosaic, it took two years to piece together this giant egg.

This Dutch art piece became a Russian icon.

This colorfully-painted tunnel links two distinct parts of a historic neighborhood.

“And the Lord said unto Johan, build for thee an ark for the end of the world is approaching.”

This steel frame is a skeletal mirage of a lost 16th-century stone building.

A set of 27 bamboo tubes creates an eerie soundscape that changes with the wind.

A monument hidden in the woods built in 1938 as a getaway for a Dutch museum curator.

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

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

A collection of biblical memorabilia.

A dream-like maze full of strange art, surreal spaces, and fantasy landscapes to get lost in.

Incredible labyrinth of man made caves.

A true Valhalla for cactus and succulent lovers.

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

A market built atop boats is one of the few floating holiday markets in Europe.

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

One of Amsterdam's narrowest houses is located right across the canal from its widest.

This small town in the Netherlands has no roads but instead, miles of canals and over 100 bridges.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.