Is it a park or a staircase?
Either way, there are great views of the Bay Bridge, Treasure Island, Alcatraz, Angel Island, and Fisherman's Wharf from the platform at the top. You can hear the sea lions too sometimes.
Jack Early Park was named for the person who first built the staricase on this previously unused land in 1962.
The entrance is at Grant and Pfeiffer.
Hours are 7:30am to 7:30pm according to Google Maps. I didn't see this information posted anywhere, but there is a gate that is probably locked at night.