Corona Heights Playground isn't much, except as a dog park, but if you walk on through the park and climb the promontory at the back, you are treated to a stunning view down onto Market Street, the Duboce Triangle and the Castro. At night it sometimes feels as though the city has a visible pulse, like a living creature, from high up on that rocky tor. It's a little hard to find, involving quite a few twists and turns in the neighborhood, but your reward is well worth the effort. If you find it on a map, be aware that what looks like the most direct route-- 15th Street off Castro, is one way the wrong way. Better to go north one street farther to 14th, turn left, left again on Roosevelt and look for the entrance when you reach Museum Way.
Warning: be careful-- there is no trail to speak of, and there are no protective barriers. If you fall from the rocks you might well roll clear to the bottom, and you won't be getting up any time soon, if at all. As with all such places where exposure is great, it's inherently dangerous, and especially so in the dark. Move with caution and don't exceed your ability or your comfort zone.
This is one of those places most San Franciscans don't even know about. Don't tell them.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.