Teufelsberg is German for devil’s mountain, a man-made hill in Berlin Charlottenburg. The hill is made out of war debris, reaching a total of 114 metres. It is the highest peak of the city. Teufelsberg was used by the British and Americans to spy on East Berlin. It was important for West Germany to know what east Germany was doing during the time of the separation. The old bugging-device was able to reach signals up to 700 kilometres away. Tours around the area have been offered since 2011. However, you can also explore the ruins by yourself. Even though there are several man-made rubble mounds in Germany and Europe, Teufelsberg is unique, as the never finished Wehrtechnische Fakultät (military technical college) is buried beneath it.