#3: Teufelsberg Listening Station (Berlin, Germany)
At the peak of the Cold War, the Allies constructed this gargantuan station on top of a hill made entirely of debris from the war. The operators then filled the facility with some of the most advanced antennas available at that time to intercept radio signals from the Soviets and East Germans. This site was considered by the intelligence community to be the most important one for espionage work in all of Europe, the crown jewel.
