The Teufelsberg (German for Devil's Mountain) is a hill in Berlin, 
Germany, in former West Berlin. It rises about 80 meters above the 
surrounding Brandenburg plain, more precisely the north of Berlin's 
Grunewald forest.
It is an artificial hill with a curious history: it was built by the 
Allies after the Second World War from the rubble of Berlin during the 
following twenty years as the city was rebuilt.
The US National Security Agency (NSA) built one of its largest listening 
stations on top of the hill, rumoured to be part of the global ECHELON 
intelligence gathering network. The hill was located in the British 
sector. Mobile Allied listening units would drive to different locales in 
West Berlin hoping to gain the best vantage point for listening to Soviet 
and East German military traffic.

Since Dec 2009