What’s the attraction: The ruins of a once-popular indoor swimming center along the coastline in San Francisco. The Sutro Baths were once the world’s largest indoor swimming pool. They were built in the 1890s by a wealthy entrepreneur in San Francisco. The pools struggled financially to remain open, and closed in the 1960s. Shortly after, a fire erupted and finished off what was already in the process of being demolished.

Now all that’s left of the Sutro Baths are cement ruins. You can walk through walkways and climb on concrete walls, though signs admonish visitors to be careful of dangerous waves.