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

Once a path for Jewish funeral processions, this unassuming alleyway is rich in local lore.

Inside this Jewish cemetery is a memorial to soldiers who deserted the German army and were executed.

Concerts, art, offices, and a café in what used to be Berlin's first crematorium.

One of the oldest cemeteries in Germany was originally used for victims of a cholera epidemic.

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

Floating swimming pool within a moored vessel.

A century-old shot ball factory tower is open to the public once a year.

The ruined remains of the airport Claus von Stauffenberg departed in his failed attempt to kill Adolf Hitler.

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."

A towering monument to war, located on a beautifully peaceful hill.

A portable, wooden replica (minus the hyphen) of Hamburg’s iconic crooked coffee shop.

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

Tiny memorials honor individual victims of the Holocaust.

One of the world's heaviest musical instruments towers within a popular urban park.

The skeletal frame of a decommissioned gas-pumping station offers breathtaking views of greater Berlin.

An eerie, derelict amusement park in Berlin.

For patriotic Russians, this memorial honoring the Soviet soldiers who died liberating Berlin in 1945 is the most sacred location outside of Russia.

This platform is now a memorial dedicated to those who were deported during the Holocaust.

A historic fire call point.

Dedicated to the European Sinti and Roma peoples murdered during the Holocaust.

Reminders of the Battle of Berlin still scar the railway.

The last remnants of a massive medieval wall that once encompassed the city of Berlin.