This abandoned NSA field station sits atop an 80 meter artificial hill in the Grunewald forest on the west edge of Berlin.
The hill has a noteworthy history: created from the post-WWII debris of desolated Berlin, it is higher than the highest natural hill (the Kreuzberg) in the Berlin area, believed to be created from the rubble of some 400,000 buildings. Buried deep within the hill a building still stands, once a Nazi military-technical college, it proved easier to bury the robust structure, than to blow it up.
For a time the hill served as a ski-hill, before it was re-purposed by as a "listening station." Believed to be part of ECHELON, a global network of listening stations, the listening station was erected on the hill and run by the U.S. National Security Agency to eavesdrop on communist East Berlin. To their surprise, they found that the local Ferris wheel, erected each year for the German-American Festival, helped relay signals and improve their listening efforts, and the US radio spooks asked if the wheel could be left up for a longer period.
The station was abandoned after the fall of the Berlin Wall, and though there were plans to resurrect it for commercial purposes, today it is a vandalized and abandoned shell. The station's elevated platforms offer incredible views of Berlin's skyline, as well as the nearby 1934 Olympic Stadium and Le Corbusier's Unité d'Habitation. Some say that the NSA built tunnels down through the mountain into the Nazi military-technical college, to serve as either an emergency bunker or escape route, however no evidence of this exists.
Wild boars roam the grounds around Teufelsberg, and visitors are advised to stay on the paths. Access to the station is officially restricted, but some visitors have found an opening in the chain link perimeter fence and used the exterior stairwell to gain entrance to the elevated platforms and radomes. Any visit to Teufelsberg should be taken with great caution -- there are potentially dangerous openings, no guardrails, and an open elevator shaft (approx. 10 stories) not to mention it being illegal.
Guided tours are available on Sundays.