The former National Security Agency Field Station on the Teufelsberg in the old British Sector of West Berlin was a listening station built and operated by the US government to eavesdrop on East German and Soviet signals. There was a small Royal Air Force presence in the form of 26 Signals Unit. Construction began in October 1963, but spying from the 'hill' began early than that. Teufelsberg, 'Devil's Mountain' in English, is an artificial hill built from the rubble that was left of Berlin after the Allies battered it at the end of World War Two. Mobile signals intelligence patrols had found that Teufelsberg was a perfect spot in the 1950's and the Field Station made permanent use of the site up until the fall of the Berlin Wall and the Reunification of Germany. In reality, the spying probably carried on until all Soviet/Russian forces left Germany in 1994. Today the site is stripped and heavily graffitied, but the iconic radomes remain, visible from many locations around Berlin.