noun

• (US) A swimming pool, especially an indoor one; a building housing one or more swimming pools.
  "This Association shall be known by the name, style and title of "The Natatorium and Institute for Scientific Instruction in the Improvement of the Physical Powers," and shall have for its object the attainment by scientific inquiry and investigation of the most desirable and beneficial mode of physical exercise, and by the scientific use of natatorial, orthopedic, gymnastic and such other physical exercise as may be prescribed by the By-Laws of this Association, to improve the health and physical condition of those who may avail themselves of the advantages of this Natatorium and Institution, in conformity with the terms of its By-Laws."