At the height of the Cold War, a hill in West Berlin known as Teufelsberg (Devil's Mountain) served as the perfect spot for U.S. and British intelligence agents to turn an unobstructed ear on East Berlin and Soviet communications. In its glory days, state-of-the-art listening towers and rotating antennas at the Teufelsberg spy station exposed the Communist Bloc's secrets to analysts and linguists from the NSA and the U.K.'s Government Communications Headquarters. After the fall of the Berlin Wall, Teufelsberg was abandoned to decay, graffiti artists and weekend partiers. The U.S. Army Security Agency (ASA) began its first SIGINT operations at Teufelsberg in 1961 after discovering that the 380-foot hill offered unobstructed collection of communication signals. As the facility grew and more buildings were constructed, the U.S. National Security Agency took over the spy operations. Photo: Matt Biddulph/ Flickr