One of the best places to go and sit by yourself.
copy and paste this tiny movie of people sliding into the pool... http://www.cliffhouseproject.com/environs/sutrobaths/1425.mpeg
This is the Sutro Baths in San Francisco.
I make it a point to go there every time I am in S.F.
There is a cave you can walk in when the tide is low - and black seaweed washes up onto the ruins.
It's a left behind bath house ghost town where hundreds of people went to show off their fancy wool bathing suits. There was an amusement park down the beach and a camera obscura up on the hill by the old Musee Mechanique and Cliff House.