At first, pedestrians walking past see an air-raid shelter, a typical reminder of Berlin's wartime history. Yet, a second glance at the massive building on Berlin's Reinhardtstrasse, near both the government quarter and the Friedrichstrasse railway station, shows the building has a lot more history than that. Christian Boros, a public relations manager from Germany's industrial Ruhr region acquired the aboveground bunker six years ago to nurture his hobby. For the last year, Boros has opened his private art collection. The somber coarse concrete walls are now contrasted with colorful light installations and glistening statues. The fortress—designed to shelter up to 5,000 people—was constructed in 1942, part of Nazi architect Albert Speer's grand vision for a new "Germania." The East German government later used it for storage, first for textiles, then for tropical fruits, such as bananas, oranges and lemons. The massive walls proved to be the perfect insulation for the fruit, a rare delicacy in communist East Germany. The building began to be dubbed the "banana bunker"—a nickname that even survived the fall of Communism and Germany's reunification in 1990. The building was declared an historic monument toward the end of the 1990s. Boros finds it important to keep the bunker's history alive for visitors.