A state-of-the-art medical facility from the Imperial era is now a derelict ruin.

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 museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

The most visited, and possibly most controversial, museum in Germany.

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

An eerie, derelict amusement park in Berlin.

Test your business savvy and play the market for cocktails at this stock exchange-inspired watering hole.

Underneath the bustling city streets, a hydroponic farm grows unique herbs in an urban oasis.

Wall Street has a new heroine, a bronze statue of a small but fierce girl.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

A hands-on traveling collection of the innovative devices of yesteryear.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

Elevated freight railway turned wildly successful urban park.

Try not to get slimed in Tribeca.

This lower Manhattan bar is set up in an old bank vault that rests beneath a skyscraper that hides even more historic splendor.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

The ruins of an abbey believed to have been founded by Charlemagne in the 9th century.

An abandoned tank sits in an empty London lot as a symbolic middle finger to local city planners.

This underpass became an unlikely piece of cinematic history after its appearance in 'A Clockwork Orange.'

This iconic high-rise residential block was one of the last to be built in the Brutalist style.

This London marker celebrates the spot where the world-famous English band was founded.

Putting the "mod" in "modular" since 2000.

Where Aleister Crowley attempted to seize the Hermetic Order of the Golden Dawn in a mask and a kilt.