Fort Schuyler, at right, is a pentagonal stone fort built in the mid-19th century at the tip of the narrow Throg(g)s Neck peninsula in the Bronx, where the East River meets Long Island Sound. Along with Fort Totten across the water in Queens, Fort Schuyler was positioned to defend the entrance to the East River against enemy naval forces trying to reach New York Harbor. Check out this awesome aerial view, and this more pragmatic map, to get a sense of the area's geography.
The fort never saw any combat, but it was quite active during the Civil War, when troops were trained here and a hospital and prison opened on the grounds. By the 1910s, however, the fort was considered obsolete, and the Army finally decided to abandon it around 1931. After a lengthy reconstruction by the federal Works Progress Administration, the property was dedicated as the new home of the New York State Merchant Marine Academy (now SUNY Maritime College) in 1938, and it still serves as the school's campus today. In addition to the conventional college buildings found here (campus map), the fort itself has actually been converted into academic space. It contains a library and the expansive Maritime Industry Museum, as well as classrooms and offices — a pretty impressive reuse of an old 19th-century fortification!