The Headlands entire grounds are a nature preserve. Sometimes the fog is so dense it's unbelievable. My first night, I went out for a late drive in the city to try to figure it out without traffic. I approached the one lane tunnel through the mountain that is the gate to the Headlands, separating it from Sausalito and the rest of civilization. It was foggy blackness except for the top edge of the hills that were a smudged line of white light cast from the city. I suddenly realized I was surrounded by about a dozen deer standing near the road, watching me and eating plants. A fog horn periodically and rhythmically blew a single note in the distant silence.