This concrete ship has had four careers - World War I tanker, floating amusement park, fishing pier, and artificial reef.

Enormous crabs, bioluminescent jellies, and other amazing creatures from the ocean’s depths—some of which are in an aquarium for the first time ever.

A tree grown from astronaut seeds which were exposed to cosmic rays.

This coffee shop lies hidden beneath a historic church.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Hidden beneath the streets of London is a secret subway that only carried mail.

Inspired by "The Starry Night" this Dutch bike path turns into a glowing work of art each night.

Berlin's old airport.

An eerie, derelict amusement park in Berlin.

Historic medieval fortified city in southwest France.

Ancient paintings known as the "Sistine Chapel of Cave Art."

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

Forget the hearse ‘cause he’s forever immortalized in a Belgian city where AC/DC performed a secret gig that pushed them forward.

A magical and peaceful ruined Cistercian abbey in what is now southern Belgium.

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

Lavish royal estate punctuated with heated greenhouses.

These ramparts, once lined with towers, were constructed in defense of Beaune.

On the grounds of a former estate in Burgundy stands an elaborate temple that is modeled after the first Tibetan Buddhist monastery.

Before this bridge was built people had to wait for the ferryman, an annoyance that, the story has it, gave the town its name.

A medieval military street hidden beneath a charming French fishing village.

One architect's organic, human-centric design has been fully realized in this alien art house.

This unusual small wind turbine in Germany has only a single rotor blade.