From wiki: On March 14, 1896, the Sutro Baths were opened to the public as the world's largest indoor swimming pool establishment. The baths were built on the sleepy western side of San Francisco by wealthy entrepreneur Adolph Sutro
. The vast glass, iron, wood, and reinforced concrete structure was mostly hidden, and filled a small beach inlet below the Cliff House
, also owned by Adolph Sutro at the time.
Both the Cliff House and the former baths site are now a part of the Golden Gate National Recreation Area
and operated by the United States National Park Service