This conical hill was built as a testing ground for an engineer known as the Glider King.

A restaurant and observation deck built in a unique broadcasting antenna.

An elevator into the Baltic Sea.

Berlin's old airport.

A 12th-century fortress containing some of Berlin's oldest buildings.

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

Started as a kitchen garden, now the second largest botanical garden in the world.

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

Massive installation of Europe's negative stereotypes.

This network of conjoined cellars was riddled with traps and supposedly allowed the townspeople to pretend their homes were deserted.

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

Street artists transformed an abandoned air vent into the beloved Star Wars robot.

These former Nazi anti-aircraft towers offer a singular view of the north of Berlin in the summer, and a sanctuary for bats in winter.

A traditional U-Bahn station in Berlin gets a string of rather untraditional benches.

Floating swimming pool within a moored vessel.

Home to 10,000 medical specimens including the remains of Rudolf Virchow's extensive collection of pathological specimens.

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

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

The world's first clock to use set theory as a measure of time required the invention of a new light bulb just to maintain its obtuse measurements.

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

This Berlin island is home to a flock of free-roaming peacocks, as well as a historic ivory folly.

Several of these strange cone-shaped bunkers can still be seen around the former Nazi headquarters.

A statue of Vladimir Illyich Lenin guards this abandoned building in the "Forbidden City."

Explore the complex ecology of this multifaceted nature preserve by riverboat.