NSA Field Station Berlin
From http://www.ccc.de/teufelsberg/teufelsberg.html

As military intelligence missions changed or were redefined, the 280th USASA  Company went through a number of transitions.  First to the 78th Special Operations Unit and later to the NSA Field Station Berlin.  The erection of the Berlin Wall in 1961 made movement within the Soviet Sector and the Soviet Zone a rarity.  In response to these restrictions, a number of diverse intelligence-gathering units within Berlin were consolidated into the large permanent FSB installation.

During the 280th ASA operational period, the manpower complement was small and maintained a low profile.  Various actions were taken to disguise the size of the unit and the identity of the personnel.  However, with the establishment of FSB and its large permanent buildings and huge antenna field, low visibility was no longer possible or practical as the staffing levels were dramatically increased.

Berlin is situated on relative flat terrain.  However, during the process of rebuilding Berlin following World War II, rubble was piled into a large hill (sometimes called Devil's Mountain) within the Teufelsberg District.  FSB took advantage of this higher geography to position long-range ELINT equipment to probe deep within the Soviet orbit.

With the fall of the Berlin Wall, the need for Field Station Berlin dwindled and it was eventually decommissioned in 1991.

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