The group is a not-for-profit, and works to preserve the underground spaces it tours, many of which are relics of World War
II and the Cold War.
"Since many of Berlin's underground structures were developed during the Nazi period, the association's main work is based around World War II, Mr. Williams said. One popular tour (simply titled the "Classic Tour") that guides you through a wartime bomb shelter is a history lesson from the perspective of German civilians living in fear of Allied bombs. The experience is made all the more unsettling by the fact that the shelter is located below the bustling Gesundbrunnen U-Bahn station, above.
Similar organizations exist in other cities, including Hamburg and Vienna. But the Berlin Underworlds Association owes its success in large measure to the continued fascination with World War II and the Cold War that followed."