Located on the western edge of San Francisco, the Sutro Baths indoor swimming-pool complex was once touted as the world's largest. The tourist attraction, developed by self-made millionaire Adolph Sutro, included seven pools that filled with seawater during high tide, an ocean pool aquarium, a massive public bathhouse, slides and diving boards.
Yet spectacular as it was, the complex, which opened in 1894, struggled to make a profit because of its extraordinary operating costs, and was eventually sold to developers in 1964. Two years later, a fire destroyed the property.
You can still visit the ruins of the Sutro Baths today at Golden Gate National Recreation Area, at the foot of the Pacific Ocean.