Photos: Pi.1415926535 · CC BY-SA 3.0 (1, 2) · lamblukas from San Francisco, United States · CC BY 2.0 (3, 4, 5)
Free, 5am to midnight. The wooden stairs are just east of the Twin Peaks and Clarendon junction, almost opposite Crown Terrace. At the top, walk north past the round tank foundation to the jagged chert for bridge-to-bridge views.