Mount Umunhum Loop

The Mount Umunhum Loop is generally considered a moderate mountain biking route, but it presents significant challenges. You'll encounter sustained climbs, particularly on Mount Umunhum Road with sections exceeding 15% grade, and steep descents on Barlow Road, some over 20%. While the singletrack Woods Trail and Mount Umunhum Trail sections are often described as flowy, the overall experience demands good fitness. Some parts can be rocky, and you might need to push your bike on steeper segments.

The terrain is quite varied. You'll start with demanding ascents on paved and gravel roads, transitioning to a 3.5-mile singletrack Mount Umunhum Trail that is generally well-maintained and runs through forested areas with numerous hairpin switchbacks. As you gain elevation, the habitat changes from chaparral to knobcone pine and coastal woodlands. Closer to the summit, the terrain opens up with steeper sections, rocky outcrops, and serpentine boulders. Descents often include steep doubletrack sections like Barlow Fire Road.

You can typically find parking at the Woods Trail Trailhead, which is a common starting point for this loop. Always check for current parking regulations and availability before your visit, especially on weekends, as spots can fill up quickly.

No, there are generally no permits or entrance fees required to access the trails within the Sierra Azul Open Space Preserve, including the Mount Umunhum Loop. However, always check the official Midpeninsula Regional Open Space District website for the most current regulations before your ride.

Regulations for dogs can vary within the Sierra Azul Open Space Preserve. It's best to check the official Midpeninsula Regional Open Space District website for specific rules regarding dogs on the Mount Umunhum Loop and other trails in the preserve. Typically, if allowed, dogs must be on a leash.

The best time to mountain bike this loop is generally during the spring and fall months when temperatures are milder. Spring offers lush greenery and wildflowers, while fall provides cooler weather and clear skies. Summer can be very hot, especially on exposed sections, and winter can bring rain, making some trails muddy or slippery. Always check weather conditions before heading out.

The most iconic landmark is the eight-story concrete radar tower, known as "The Cube," at the Mount Umunhum Summit. This Cold War relic offers spectacular 360-degree views. You'll also find interpretive signs along the trail detailing the area's natural environment and history, including the ruins of a cabin belonging to the "mysterious Lady of Mount Umunhum." The mountain's name itself, "Umunhum," is an Ohlone word meaning "resting place of the hummingbird."

While much of the trail is under tree cover, the Mount Umunhum Summit provides truly spectacular 360-degree panoramic views. On a clear day, you can see across Silicon Valley, all the way to San Francisco, Monterey Bay, and the Pacific Ocean. Other prominent peaks like Mount Hamilton and Mount Diablo are also visible.

Yes, this route incorporates sections of several other trails. Notably, a significant portion of the loop is part of the Bay Area Ridge Trail - 03 - South Bay. You'll also ride on sections of the Woods Trail, Barlow Road, and various segments of the Mount Umunhum Trail itself.

Almost. While the majority of the loop is open to mountain bikes, the final 0.2 miles directly to the Mount Umunhum Summit are restricted to hikers only. You'll need to dismount and walk your bike for this short section to reach the very top and the iconic "Cube."

Given the trail's length (over 22 km) and significant elevation gain (over 670 m), it's crucial to bring plenty of water, snacks, and appropriate gear. A helmet, gloves, and sturdy mountain biking shoes are essential. Consider carrying a repair kit, spare tube, and a first-aid kit. Layers of clothing are recommended due to changing temperatures with elevation. Don't forget your phone for navigation and emergencies, and perhaps a camera for the summit views.