A natatorium (plural: natatoria) is a building containing a swimming pool. In Latin, a cella natatoria was a swimming pool in its own building, although it is sometimes also used to refer to any indoor pool even if not housed in a dedicated building (e.g., a pool in a school or a fitness club). It will usually also house locker rooms, and perhaps allied activities, such as a diving well or facilities for water polo. Many colleges, universities and high schools have natatoria.
Flushing Meadows Natatorium, Queens, New York