A swimming pool is an artificially enclosed body of water intended for recreational or competitive swimming, diving. Many also come to the swimming pool to enjoy water slides, water aerobics classes, cooling off on hot days, or perhaps warming up in the hot tub on cold days. Swimming pools can be constructed either above ground, or right into the ground. Artificial swimming pools are known to have been built by the ancient Greeks and Romans who used them for athletic training in the palestras as well as for nautical games and military exercises.
Swimming pools are often found as part of a larger leisure centre or recreational complex. These centres often have more than one pool, e.g. an indoor heated pool, an outdoor saltwater or unheated chlorinated pool, a shallower 'children's pool', and a paddling pool for toddlers and infants. There may also be a sauna area. In the swimming pool area and/or in the sauna area there may be one or more jacuzzis.
Many public swimming pools are rectangles either 25 m or 50 m long, but a backyard pool can be any size and shape desired. There are also very elaborate pools, with artificial waterfalls, fountains, splash pads, wave machines, varying depths of water, bridges, and island bars; they may belong to a hotel or holiday resort.