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9. RAF Menwith Hill – United Kingdom
Despite its location in North Yorkshire, this Royal Air Force base is run mainly by the NSA. The base has grown in size and importance in recent years, becoming vital for surveillance operations. Those giant geodesic golf balls are called radomes, and they protect radar equipment which monitors satellites. Although it was designed to eavesdrop on Soviet enemies during the Cold War, it now monitors everything from phone calls to wifi traffic.