This Czech military museum is home to pink tank that was once a symbol of art and political rebellion.

An unusual bronze bus shelter is actually an art installation commenting on the city's history with the Nazi party.

Massive installation of Europe's negative stereotypes.

Underneath the city that invented pilsners are a series of historic tunnels that have been storing beer for centuries.

A Jenga-style cylindrical tower of books that appears to go on forever.

What looks like a suicide in progress is actually a statue of Sigmund Freud.

Countless grotesque faces stare out from this eerie Prague art wall.

An eerie, existential museum dedicated to the author of "The Metamorphosis."

An existential riddle in the world's largest ancient castle.

The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

The ruins of a 13th-century monastery that long served as a place of refuge from wars and raids.

Climb around the high waterfalls on series of iron ladders and bridges within the wildest gorge in the Slovak Paradise.

An unusual cave filled with rare alien-looking aragonite formations.

An abandoned 19th-century iron factory perched along the outskirts of an idyllic village.

This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

Boats must transform into railroad cars to navigate this Polish canal.

These massive moving sand dunes have swallowed an entire village and are still on the run.

The last municipal pneumatic post system in the world was in operation for over 100 years, and may run again.

An architect transformed this abandoned cement factory into his castle-like workshop.

This religious complex carved into a cliff is steeped in legends of miraculous stags and the Holy Grail.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

Natural stone arches form a walkable "cathedral" at low tide, then disappear entirely when the water returns.