Consult most any Mount Diablo hiking guide, and the “Grand Loop” will likely be a featured trek. It’s just widely accepted by nature enthusiasts that this particular route showcases many of the perks that the mountain has to offer. The journey is teeming with stunning views, diverse flora, a healthy population of raptors, and plenty of terrestrial wildlife.
Traversing through multiple terrains in a 360 degree loop around the mountain and ending at the summit, the Grand Loop really embodies the essence of Mount Diablo.
The staging point of the hike is located at Juniper Campgrounds which provides a parking area overlooking the San Ramon Valley. From there you can walk toward the back of the campsites where your first trail awaits. It’s just past site 23; look for a wooden fence and marker for Deer Flat Road.
Juniper Campgrounds is two and a half miles up Summit Road, which is accessible from any Mount Diablo entrance. Directions to the park with a map can be found at this link. Also be sure to pick up a park pamphlet (map included) when you pay the $10 entrance fee at the gate.
Once you make it to Deer Flat road, follow the trail for three quarters of a mile. Make a right at the first fork you come to, and travel downhill until you hit Meridian Ridge Trail.
Much of this portion of the hike is dominated by shrubs and rocky terrain, but the trail soon becomes shaded by pine trees. Their fragrant needles mix with the aroma of wild rosemary to create a pleasant scent.
Meridian Ridge Trail will come to a junction with Eagle Peak Trail and Bald Ridge Trail. The narrow path that works its way uphill is Bald Ridge Trail, your route for the next mile and a half of the journey. This portion is steep and slippery with small rocks, so navigate your way carefully.
Bald Ridge will lead to another junction where you can follow North Peak Trail left or right; turn right onto the narrow route. This section of trail provides amazing views of unsettled land, and interesting rock formations which dot the landscape.
North Peak Trail meets up with Summit Trail which shadows a paved road up to the park’s museum and observatory. After about half a mile of uphill hiking you can exhale deeply upon reaching the summit.
If the day is clear enough you will be able to see the Golden Gate Bridge, Mounts Hamilton, Saint Helena and Lassen. Rivers, islands, valleys and the delta are just a few other natural features to admire. It’s also astonishing to get a birds view of the network of towns and cities that make up the Bay Area. Viewing this mix of nature-created and man-made displays can be a humbling experience.
Once you’ve thoroughly absorbed the vistas from the summit, head back down Summit Trail. Walk across the lower summit parking lot which is where Juniper Trail descends down the mountain. This will lead to Juniper Campground and your vehicle.
The hike is around eight miles overall, and covers over 2,000 feet in elevation change. While not easy, it is incredibly rewarding. Embark on Mount Diablo’s Grand Loop and you will not be disappointed.
A few things to make note of: This is a fairly grueling trek; I wouldn’t recommend it if the temperature is 90 plus degrees. Sections of the trail are composed of small, loose rocks, and can be slippery. Make sure to wear hiking shoes with good tread. The hike can be extended to include Eagle Peak and North Peak if you are looking for more views and a challenge. Lastly, the Mount Diablo summit museum and observatory are currently closed for repairs, but the views from outside the facility are still spectacular.
At a Glance:
Mount Diablo State Park
Address: Juniper Campround, 2.5 miles up Summit Road, Mount Diablo
Hours: 8 am - Sunset
Best time to visit: Any day with clear skies and moderate temperatures
Great for: Vistas and a wide variety of flora and fauna.
Could be better if: The day is clear enough to see the Golden Gate Bridge from the summit, and you bring binoculars.