A couple of months ago, I have signed up as a volunteer to lead guided mountain bike rides on a trail managed by the San Francisco Public Utilities Commission. This Fifield-Cahill trail is open to public since 2003 but only upon a reservation and as a guided tour. The events include hiking, trail running, horse rides and biking. There is a lot of information about this natural resource on the SF PUC website here:
There is an online reservation system, as well as a trail map (you have to click on the "Become a volunteer trail leader" link to see a PDF of the trail and surrounding area.
The trail is 10 miles long from gate to gate, south entrance on Hwy 92, north entrance just south of the San Francisco discovery site in San Bruno accessed from Sneath Lane. On the northern end, it connects to the Sweeney Ridge trail and Baquiano and one more trail to Pacifica (all managed by the GGRNA).
During the training day, which included a van tour of the whole trail, I have learned lots of new information about this watershed, the water system that feeds 2.5 million people in SF and the Peninsula. The scenery along this trail is amazing, with views of the Pilarcitos Reservoir, which I think cannot be seen from anywhere else, Montara Mountain, Pacifica, the Pacific coast in the west, the Bay, SFO, San Bruno Mt. etc in the east.
These three pictures show the Pilarcitos Reservoiur and Montara Mt. on the horizon (with the radio towers):
The trail surface is a very well draining fine gravel. The trail is in an excellent condition, which means no technical mountain biking, but a fast ride and a good workout, too, since the trail is far from flat. Eventually, this trail is supposed to be connected to Montara Mt. trails, which would make a pretty strenuous but fantastic loop possible.
So I am looking forward to show this place to bikers, my friends and colleagues and hopefully go for a ride or trail run there few times a year.