Hinsdale is located in the Berkshire Hills, with most of its population located in a valley along the East Branch of the Housatonic River, whose origin is just south of the town line. Much of the land around the river south of the town center is part of the Hinsdale Flats Wildlife Management Reserve, and is generally a swampy area. There are four reservoirs within the town (Belmont, Plunkett, Cleveland Brook and a portion of the Windsor Reservoir), as well as part of Muddy Pond in the south and most of Ashmere Lake along the Peru town line. The town, which contains the peak of Tully Mountain along the western border, is traversed by a portion of the Appalachian Trail, which crosses the mountain. The town also has several summer camps and a country club.