The brisk blue waters of Round Valley Reservoir attract swimmers, boaters, fishermen, picnickers and campers to its scenic shore.

The Round Valley Reservoir swimming area was created by the construction of an earth dam across a narrow waterway on the west side of the reservoir, separating it from the main part of the reservoir. The reservoir covers about 2,350 acres and is approximately 180 feet deep, the second deepest lake in New Jersey. It has a water capacity of 55 billion gallons. The reservoir is stocked with lake trout.

Round Valley is the only state park that offers wilderness camping. The campsites on the eastern side of the reservoir are accessible only by hiking or boating. The campers' parking lot is three miles away from the nearest site, reachable by a steep and rugged trail. Cross-country skiers and sledding enthusiasts congregate at Round Valley in the winter months.