What is now a beautiful ruins directly north of Ocean Beach, San Francisco was once the world's largest public indoor swimming pool.
The Hidden Cave
What is even more fascinating.. after the pool lost popularity an ice skating rink was built over the pools in hopes of gaining mass visitors again, however the ice skating rink never took off. In the 1960's developers planned to built a high rise there (of course, right? ha) but after another fire the plans fizzled away and what remained is what we see today.
Sutro Baths
This is a perfect sunny day exploration. Be sure to find the hidden cave - seriously one of the coolest places I have seen and been inside of - throw on those sneakers to experience a stunning hike along the Pacific Coast towards the Golden Gate Bridge then finish off with a delicious bite over at Cliff House (be sure to eat in the bistro on the top level, much cooler) and enjoy the views of the kite surfers in the ocean. Ahh what a day.. this might need to happen today :)
Enjoy!