Grandview Park is a small hilltop park in San Francisco's Golden Gate Heights. Wikipedia says it is bounded by 14th and 15th avenues and Noriega Street and covers about 4 acres.
A hill made of ancient seafloor
The summit is an outcrop of Franciscan chert, a hard rock formed from the remains of tiny ocean organisms. SFGate's Urban Outings column estimated the rock at about 140 million years old. Both sources say longtime residents call it Turtle Hill.
Rare plants
Wikipedia says the hill supports native plants including the endangered Franciscan wallflower and the dune tansy, along with a stand of Monterey cypress. To protect the plants, visitors are asked to stay on the paths.
How to get there
The best-known approach is the 16th Avenue Tiled Steps at Moraga Street. SFGate says more than 220 neighbors sponsored tiles for that mosaic. From the top of the tiles, keep climbing toward the summit. SFGate also describes a 15th Avenue staircase of about 160 steps.
For transit, SFGate suggests taking the N-Judah to 16th Avenue and walking up, or riding the 66 Muni bus, which stops at 16th Avenue and Moraga.
SFGate describes 360-degree views from the summit, taking in the Pacific Ocean, downtown, Golden Gate Park, Sutro Heights, the Marin Headlands and Lake Merced. Nearby are the Hidden Garden Steps.