Fifield-Cahill Ridge Trail in San Bruno, CA, is a 10-mile section of Bay Area Ridge Trail that can be hiked only by prior registration: check out SFWater Website for list of events and other details. To cover the entire trail, you may sign up for a 13-mile one-way hike that combines three miles of trails in Sweeney Ridge with ten miles of Fifield-Cahill Ridge Trail.

Best Months to Visit: Several miles of the trail are in the open. So avoid summer days.