The 20-mile causeway that separates the Netherlands from the sea.

Go inside a revolutionary, cage-less zoo where 70 species of monkeys roam free alongside their human visitors.

This giant wire frame man sculpture is crouched in contemplation.

The works of poetry's biggest names grace the walls of the city of Leiden, all carefully painted by hand.

A trio of red, white, and blue stones embedded in the streets of Leiden are markers of medieval territory and law.

A former plague hospital turned medical museum.

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

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

This bridge was constructed from the rubble of the infamous Bastille.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

The celebrated eyesore created by starry-eyed sweethearts.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

The oldest stone house in Paris was built by its most famous alchemist.

A magical, macabre wax museum, beloved by locals, uses real artifacts to depict an assassination from the French Revolution.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

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

A beautiful maze marks where three countries meet.

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

Incredible labyrinth of man made caves.

A radio telescope for listening to the stars, based in one of the cloudiest countries in the world.

The history of sea-faring refuse and disaster is on cramped display in this Netherlands folk museum.

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

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