A walkable map of the world, made from soil and stone by one man.

Digger attempting to hide itself under 300 tons of rubble.

A natural wonder in south Denmark.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

Old Danish castle immortalized in Shakespeare's Hamlet.

From Coke II to Google Glass, this exhibit features some of the most spectacular commercial flops.

This Swedish astronomical clock was in storage for almost a century before its glorious workings were put on display once more.

Rocks carved with biblical passages in the 1800s.

The Frank Zappa fan club erected this monument to their prog-rock hero to mark a new era of post-Soviet Lithuania.

Underwater roads undetectable from the surface used for escape routes from foreign invaders.

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

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

This antique thermometer honors the creator of the first universal temperature scale.

These rare statues are one of the few remaining material witnesses to Old Prussian culture.

A huge wooden clock that is so beautiful its creator was forcibly blinded.

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

This Communist-era residential block is one of the longest residential building in Europe.

The site of the first battle of World War II.

This encrypted monolith protected a secret of Norse mythology by hiding in a church wall for over a millennium.

An eclectic sculpture park rises atop a giant pile of ashes in Sweden.

This intricately spiralling forest was created as a monumental work of art.

Not quite the cultural gateway between China and Sweden its designer imagined.

The church's remarkable frescoes incorporate Finnish artist Hugh Simberg's trademark themes of death and the supernatural.

You would never guess that before World War II this lonely field was a bustling German city.