Mountain biking in San Francisco. You've got the trails around Mt. Sutro, a few trails in Golden Gate Park and the trails of McLaren Park. It's not bad considering the city is 7 x 7 miles. This doesn't count the illegal trails of Mt. San Bruno, which I have yet to explore. For a quick dirt fix I'll hit up any one of the three parks if I'm pressed for time. In the photo above I'm overlooking Mt. San Bruno from the east end of McLaren Park. I just started riding the trails here, and only got to do the lower half of the park before having to head to work.