The world's second-largest sundial, made entirely out of stone.

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

Horrifically creative torture devices and shame punishments line the walls of this chilling museum.

Dress up like a miner and take a slide into the disco-lit depths of this once foundational salt mine.

It's always summer at the beach inside this former airship hangar.

One of the most easily accessible examples of the rare 1960s UFO houses.

A Black Forest cuckoo clock theme park features one timepiece big enough to walk inside.

Puppet theater and museum holding a collection of more than 300.

An elevator into the Baltic Sea.

The first (but not only) upside-down house in Germany.

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

The prototype for all Nazi concentration camps.

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

This little museum is making sure that the art and history of the graffiti sticker is not scraped from history.

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 tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

This "floating railway" is one of the world's oldest monorail systems.

When the rain falls, this drain system turns into a musical instrument.

A stairway to heaven, or to nowhere at all.

Art and a pun, all in one.

From toys to kettles to scientific instruments, this German museum celebrates the beauty of 20th century design.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

A striking 12th-century-style castle built on the edge of a cliff.

This World War II bunker now survives as a documentation of the Nazi regime and war crimes.