In 1830, cemetery workers in Cham unearthed a chamber housing thousands of skeletal remains from the 13th century, which can still be viewed today.

This former steel and coal plant is now a neon-lit industrial fantasia.

This German bone house contains the remains of some 20,000 souls.

A long spiraling walkway winds through the woods, and around a copper beech tree at the center.

No need to strap in for a "ride" on this walkable roller coaster.

What started as a tongue-in-cheek shrine is now a full-blown museum celebrating "The Hoff" and his longtime love affair with Berlin.

A stairway to heaven, or to nowhere at all.

An intricate and amazing house built by architect Karl Junker.

Art and a pun, all in one.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

An eerie, derelict amusement park in Berlin.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

This bike path traverses the treetops.

Head underground and take a tour of the city's working sewer system, and see the underground river Senne, which defined Brussels for centuries before being covered in the 19th century.

A maze of crosses marks the jumbled divide between the Netherlands and Belgium.

The "stairway to heaven" lookout tower was built to resist weather, arson, and the laws of physics.

Rare wooden escalators lead deep down into an otherwise staggeringly monotonous tiled tunnel.

A terrific purveyor of natural history objects and curios.

A statue of the second-tallest Dutchman in history.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

New York City's smallest piece of private property.

Try not to get slimed in Tribeca.

These crumbling Nazi artillery bunkers are now fair game for massive graffiti projects.