In Berlin, you will be able to find an abandoned NSA field station. The landmark, known as Teufelsberg or Devil’s Mountain, is set on top of an artificial hill made using the rubble of 400,000 buildings destroyed during World War 2. This structure was essentially used by the US to eavesdrop on East Berlin during the Cold War. However, after the Berlin Wall was destroyed, the center was completely abandoned - but not destroyed.
Today, visitors can walk around the remains of the buildings, and it's a popular spot for industrial and alternative photography.