Fort Independence, a pentagonal five-bastioned, granite fort built between 1834 and 1851, is the dominating feature of Castle Island. This 22-acre urban park is connected to the mainland by both pedestrian and vehicular causeways. Pleasure Bay, the M Street Beach and Carson Beach form a three mile segment of parkland and beach along the South Boston shoreline of Dorchester Bay. Carson Beach offers some beautiful views and great public amenities: a rehabilitated Mothers' Rest, public restrooms, exhibit space, first aid and lifeguard functions, while the outdoor courtyards allow space for passive recreation. Carson Beach also features a walkway which allows one to walk, bike, or run along the water's edge from Castle Island to the Kennedy Library.