If you, or anyone else is interested there is a wonderful underground complex south of Berlin, Germany, called Zossen Wunsdorf. Disguised above ground by 'houses' of solid concrete which deceived the eye of pilots flying over. The gardens were maintained, washing was hung out and flowers grew in window boxes! It was a 4+ floors down, military command centre with its own daily train to Moscow, such was its importance. Used by East Germans and Soviets it it the most fascinating bunker township and there were daily tours when I visited in 2005.
Hazel.