The Connecticut Valley Railroad Roundhouse and Turntable Site is a former railroad facility located in Fort Saybrook Monument Park off Main Street in Old Saybrook, Connecticut. The roundhouse and turntable were built in 1871 by the Connecticut Valley Railroad, which was later acquired by the New York, New Haven and Hartford Railroad. The rail line operated from its founding until 1922. The rail facilities are built partly on the archaeological remains of Fort Saybrook, the main fortification of the 17th-century Saybrook Colony, and are the only surviving remnant of what was once a large facility, with an icehouse, coal bin, steamboat dock, depot, and signal tower. Archaeological remains of these other facilities are believed to lie under other parts of the park and adjacent properties. The exposed facilities were excavated in 1981-2.