Great hiking and mountain biking close to North Bay towns

Gary Giacomini Open Space Preserve. Photo by Craig Solin
Photo by Craig Solin

Park Information

HIGHLIGHTS: Located east of Fairfax on the flanks of San Geronimo Ridge, this 1,500-acre Marin County preserve is both an open space treasure in its own right and a gateway to 25,000 acres of wildlands stretching to Mount Tamalpais.

Managed by the Marin County Department of Parks, the preserve supports a tapestry of distinct ecosystems: mixed coniferous forest (including redwoods), oak and madrone woodlands, chaparral lands and grasslands. Dwarf Sargent’s cypress trees eke out an austere existence among the rocks along the ridgeline, sharing their territory with rare Marin manzanita. Wildlife is remarkably abundant. Along with the ubiquitous black-tailed deer, mountain lion and bobcat prowl these environs, and the fire roads and trails along the ridges are dotted with coyote scat. The preserve’s high routes are a perfect place to observe the North Coast’s famous fall raptor migration. In short, given its proximity to the great cites of the Bay Area, the preserve is remarkable for the sense of wilderness it conveys to the visitor.

ACTIVITIES: The preserve is a great hiking and mountain biking venue within an easy drive of San Francisco, the East Bay and the North Bay. Much of the ridgeline is exposed, and can become quite hot during sunny days. Make sure to bring plenty of water and a hat. Horseback riding is allowed on designated roads and trails.


CAMPGROUNDS: None. RV day-use parking is limited because it’s on city streets.

TRAILS: There are about 10 miles of fire roads and trails. Fire roads are the primary means of access for the preserve, but they are highly scenic. Don’t expect much in the way of signage; there’s little if any. The fire road along the top of San Geronimo Ridge is the signature hike/bike ride for the preserve. This 4- mile out-and-back route starts at the open space gate at the end of Conifer Way. Keep to the right on Conifer Fire Road at mile 0.80, where a trail merges. At mile 0.91, merge right on San Geronimo Ridge Fire Road, until you come to an observation point at mile 2.10. The views along the way – of Sugarloaf Peak in Sonoma County to the north, Mount Tamalpais to the south, Kent Lake downslope – are stupendous.

As noted, the exposure of this route can make for uncomfortably hot hiking. Late fall and spring typically provide the most pleasant temperatures.

MUST-SEE UNIQUE FEATURE OR SEASONAL HIGHLIGHT: A large vein of serpentine underlies San Geronimo Ridge, resulting in an abundance of rare “serpentine endemics” – trees, flowers and shrubs uniquely suited to growing in soils low in nutrients and calcium but high in magnesium. The prime example: pygmy forests of Sargent’s cypresses along the preserve’s ridgeline. Following wet winters, Giacomini’s spring wildflower displays can be truly spectacular.

HIDDEN GEM: In the rugged outcrops along the ridge, look for “rock gardens” of Tamalpais and Tiburon jewelflowers and other small, delicate wild blooms.

FEATURES ACCESSIBLE TO PEOPLE WITH DISABILITIES: The trailhead entrance is accessible; trails are rough.

DOGS: On leash on single-track trails and off leash on fire roads if under voice control and owner has leash


SPECIAL EVENTS: Visit the schedule of events for Marin County Parks and protected lands – including the Giacomini Open Space Preserve.

MORE INFORMATION: Go to the Marin County Parks website or call (415) 473-6405.

PLACES TO EAT AND STAY: The Woodacre Market and Lagunitas Market both have excellent deli sections, and are nearby. Fairfax, San Rafael, Mill Valley and Sausalito offer additional options for dining and lodging.

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