Tucked into a hillside between houses near the Castro, two smooth concrete slides drop steeply through a small park. There are no signs, no tickets, and no attendants -- just the slides, a set of stairs back to the top, and whatever cardboard you remembered to bring. Sitting on cardboard is essential; without it you will not slide and your trousers will not thank you.
The slides are surprisingly fast and great fun for adults and kids alike. Finding them is part of the charm -- look for the stairway off Seward Street between Douglass and Castro. Open during daylight hours only.