Teufelsberg is 80 meters tall and is made of 26 million cubic meters of rubble.
It sits on the site of a former Nazi military training school designed by Hitlers chief architect Albert Speer.
In fact, the ruins of the school are still buried underneath.
These women came to be known as Trummerfrauen or rubble women for their efforts.
At first mobile listening units were deployed at Teufelsberg to listen into communications from Russian-controlled East Germany.
In 1963, permanent structures were erected.
It wasn’t very discreet.
There were five large radar domes, some of them perched atop three and six-story towers.
Situated high above all obstructions, the Teufelsberg enjoyed excellent reception in most radio bands.
Radio reception even mysteriously improved, to NSAs surprise, during certain times of the year.
The NSA talked the festival organizers into keeping the wheel in place long after the festival was over.
Teufelsberg is currently used as a recreational area.
Berliners meet here in the summer for picnic, kite flying, paragliding and mountain biking.
In winter, the hill becomes just right for sledging and snow boarding.
The facility itself is slowly crumbling away.
Thieves and vandals have stripped the site of any valuable materials that remained after the spies left.
All available surface is covered with graffiti.
