A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".

An abandoned stretch of elevated road in the middle of the Brazilian jungle.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

When German-Iraqi relations broke down, this embassy was vacated post haste.

If they push on just the right spot, even the weakest person can move this titanic boulder.

The haunting concrete remains of a Nazi pebble crusher can still be found in this small French commune.

An abandoned lighthouse off the beaten path, one of the few surviving pre-World War II Japanese structures, offers a beautiful view.

The tragic reality of a town riddled with rumors of haunts, chemical spills, and serial killers.

An abandoned lighthouse awaits its destiny: being buried under shifting sand.

A perfectly circular stronghold constructed in the 10th century is now a nucleus of Viking culture housing a museum, village, and reenactment of an epic Viking battle.

This Danish rock field is actually a sprawling ancient cemetery holding the bodies of 700 Vikings.

This huge industrial sculpture looks like a UFO and a factory had a baby.

The original home of the Lego has a huge amusement park dedicated to the iconic plastic toy.

Old Danish castle immortalized in Shakespeare's Hamlet.

Mounds, rune stones, and a 1,000-year-old church, left behind by Denmark's first two kings.

Four alabaster giants contemplate the tides on the shore of Denmark.

This quiet bird sanctuary on the Danish coast is home to something not usually found in a conservation area: hunters' cabins.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

Europe's largest natural bridge has a 19th century royal chateau built into its side.

This painted Lego bridge is the product of over a century of locomotive history.

A floating cat sanctuary on an Amsterdam canal.

The great Danube river starts here.

Germany's Glienicke Bridge has a shady history of clandestine meetings, espionage, and spycraft.