I found Coit Tower quite by accident. I was walking in the North Beach neighborhood, and came upon a charming street lined with townhouses. I turned up the street and climbed to the top, and then walked up a small path to a major road. Across from the road, I could see a huge tower, with a path leading up the hill to it.
Atop the hill, there were tons of people. San Francisco has provided coin-operated binoculars. From here, you could walk around the hilltop and see most of the city: Alcatraz, Bay Bridge, Golden Gate Bridge, the skyline.
It is free to enter the base of the tower and view the frescoes that depict life in San Francisco. There was a fee to climb to the top. No matter, I had climbed quite enough to reach the tower and the view from the base is stunning enough, thank you.
There was a snack bar and some ice cream stands at the top of the hill for refreshments.