Mansfield Hollow Lake
Mansfield Hollow Lake is a reservoir resting on the border of Windham County and Tolland County, Connecticut. It was created by the Mansfield Hollow Dam and is entirely contained within Mansfield Hollow State Park. Designed and constructed by the United States Army Corps of Engineers, this dam substantially reduces flooding along the Quinebaug, Shetucket, and Thames rivers. Construction of the project began in 1949 with completion in 1952 at a cost of US$6.5 million. The Mansfield Hollow reservoir is located within the Shetucket River Watershed and is part of the Thames River Basin. Access to the site is available from US Route 6 and State Route 195 .

The project consists of a rolled earth fill dam with stone slope protection 12,420 feet (3,790 m) long and 68 feet (21 m) high. The spillway comprises a concrete weir 690 ft (210 m) in length. The weir's crest elevation is 16 feet (4.9 m) lower than the top of the dam. The permanent lake at Mansfield Hollow Dam, Naubesatuck Lake is 450 acres (1.8 km 2) in size. The flood storage area for the entire project covers about 1,880 acres (7.6 km 2) in the towns of Mansfield, Windham, and Chaplin, Connecticut. The entire project, including all associated lands, covers 2,472 acres (10.00 km 2). The Mansfield Hollow Dam can store up to 16.1 billion gallons of water for flood control purposes. This is equivalent to 5.8 inches (150 mm) of water runoff from its drainage area of 159 square miles (410 km 2).

Mansfield Hollow State Park is located on Bassett Bridge Road in the town of Mansfield. It offers a shaded picnic area and many miles of hiking and cross country ski trails. This recreation area is open daily from sunrise to sunset. There is no entrance fee. This area is managed by the State of Connecticut Department of Environmental Protection. Mansfield Hollow Damsite is located on Mansfield Hollow Road in the town of Mansfield. Here, visitors can picnic on the lawn both downstream of the dam and on the lake side of the dam. Open year-round, sunrise to sunset. No entrance fee. The top of the dam itself is popular for walking, jogging, and biking. The west half of the dam is approx. 1-mile (1.6 km) long, the east half is almost 2 miles (3.2 km) long. Parking is available at the State Park, Damsite, Commuter Parking Lot on US Route 6, and athletic field parking lot on State Route 89. A boat launch is located on Bassett Bridge Road in the town of Mansfield, 1/2 mile east of the State Park entrance. No fee. The dam runs alongside Windham Airport.