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

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

A crumbling bakery where forced laborers from the nearby concentration camp toiled to feed their fellow prisoners and Nazi soldiers.

The site of a concentration camp where inmates were made to take part in one of the largest counterfeiting operations in history is now hauntingly empty.

Gardens representing parts of Asia, Europe, and the Mid East are tucked away among the Soviet-style buildings in East Berlin.

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

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

An abandoned NSA listening post on Berlin's "Devil's Mountain."

Art installations, derelict railcars, and endangered grasshoppers all call this south Berlin park home.