North Truro Air Force Station, Massachusetts

One of the oldest early warning radar stations in the country, this remote 125-acre site on the coast of Cape Cod was part of the first SAGE/Whirlwind system tests, conducted by MIT's Lincoln Lab in the early 1950's. It went on to become an Air Force early warning and Ground-Control Intercept radar station, with as many as 90 buildings and a staff of 500. The Air Force mothballed the facility in 1985, and completely moved out (though a 20-acre parcel was turned over to the FAA, which operates a long range radar station there called the North Truro FAA Radar Site). In 1994, the National Park Service took control of the property, incorporating it into the larger Cape Cod National Seashore, while simultaneously declaring most of the site a public park. Since then, efforts have been ongoing to transform the site into a facility called the Highlands Center, which will be used to host art, scientific, and educational programs. On an adjacent property lies the Jenny Lind Tower, a 70-foot tall stone structure resembling a castle, named after the singer known as the Swedish Nightingale, who once sang to a crowd from this tower, when it was located at a South Boston railroad station. It was moved to the site in 1927.