A "banana bunker" figures in today's Geo Quiz.

The so called banana bunker is an unusual landmark in the German city were looking for. The Nazis built this massive shelter during WWII to protect German citizens from air raids.

Art bunker: The old bunker at Reinhardstrasse 20 was built in 1942 as part of Nazi air raid shelter. Now its begun a new life as home to a private art collection.

After the war, the Soviet occupiers used the impenetrable bunker as a prison for Nazi war criminals. Later, during the Communist era, locals made use of this concrete vault to store fruits and vegetables imported from Cuba, hence the nickname the "banana bunker".

After 1989, this East German venue morphed into a notorious sex and techno club. Now the Nazi bunker has yet another lease on life. We'll tell you about it when we reveal the answer.

For now, name the German city that's home to this 5-story concrete bunker as well as a more famous landmark, the Brandenburg Gate.