On a hill called Teufelsberg (Devil's Mountain) near Berlin, an abandoned facility complete with "radar domes" stands. It was once used as a listening station for the US to intercept Soviet communications, and then abandoned when West and East Berlin were reunited. It was built over top the remains of a Nazi war college. Exploring this station is difficult, as it is deteriorating. One of the dangers is an open 10-story elevator shaft! See a set of pictures at Environmental Graffiti. Link
(Image credit: Flickr user Nate Bolt)
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http://www.dw-world.de/dw/article/0,2144,1575535,00.html