When you’re this close to Mount Diablo, when it seems as if you could just reach out and touch it, why not just hike or run on the vertically challenging trails there?
Well, maybe you’re tired (physically and mentally) of unceasing uphills. Maybe you just want a nice jaunt in the foothills.
In that case, Shell Ridge Open Space, in the shadow of the devil mountain, is a viable option. It’s a 9-mile loop through the heart of Shell Ridge, a trail system of 31 miles with paths snaking off every which way, all well marked. Walnut Creek was smart enough to save this swath of oak-studded foothills from the housing developments that engulfed the rest of the area.
Highlights include the looming boulders at Castle Rock, near the start; the Briones-Mount Diablo Trail, a well-manicured, rolling-hill fire road, with the historic Borges Ranch a brief detour on the right; as well as the Ridge Top Trail. You’ll do some climbing in a steady but not-exactly-lung-busting mile on the Ridge Top Trail, but can make a slight detour and rest on a wooden bench on the hilltop before returning to the trail to tackle some switchbacks along the side of the hill.
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The views of the Walnut Creek-Concord-Danville area are, well, expansive. Lots of housing tracts, but also lots of trees.
Shell Ridge Open Space
Directions to trailhead: Take I-80 to I-680 over the Benicia-Martinez Bridge. Take the Walnut Creek exit and merge onto North Main Street. Turn left on Ygnacio Valley Road. Turn right on Walnut Avenue (not Walnut Boulevard, which is a mile before). At a traffic circle, veer right onto Oak Grove Road-Castle Rock Road. The Castle Rock Recreation Area parking lot is on your right.
Route: From south of the parking lot, take the Castle Rock Trail for 0.5 miles, turn right on the Shell Loop Trail. After 0.2 miles, turn left, staying on Shell Loop. At the next junction, turn right onto the Briones-Mount Diablo fire road. After 1.8 miles total, turn right onto the Ridge Top Trail. Follow for about a mile uphill and down switchbacks to a cattle gate. Cross the Costanoan Trail and do a semicircle on the Ridge Top Trail, winding up back on the Costanoan, 100 yards west. Cross Costanoan and the cattle gate, and resume on the Ridge Top Trail. Before the water tank, make a sharp right, staying on the Ridge Top Trail. Turn left on the Briones-Mount Diablo Trail, then a right on Fossil Hill Trail. Take it around the hill about 0.3 miles, then turn right on the Indian Creek Trail. Take Indian Creek for 1 mile, right on the Briones-Mount Diablo Trail. After a 0.7-mile uphill, stay straight on the trail to the Shell Loop and retrace steps to the trailhead.
Shorter route (6 miles): At the Ginder Gap Loop Trail crossing on the Ridge Top Trail (about 3 miles into trek), turn left and take Ginder Gap past Willow Spring Pond to the Briones-Mount Diablo Trail. Turn left and return to the trailhead on Briones-Mount Diablo and Shell Loop.
Longer route (12.5 miles): After completing the Indian Creek Trail segment, go right onto the Briones-Mount Diablo Trail and, after a half-mile, turn right on the Sugarloaf Shell Ridge Trail. Go downhill to the second signed post for the Twin Pond Trail. Turn left on Twin Pond (just after a trailhead) and go 0.3 miles before making a sharp right turn, staying on Twin Pond. At the Joaquin Ranch junction and trailhead, turn left on Twin Pond and take it past the Sugarloaf crossing, going right, then left, then wrapping around the pond. Turn right at the Sugarloaf junction (which you initially passed) and head uphill to the Briones-Mount Diablo Trail. Return the way you started.
Toilets: At Castle Rock trailhead
Parking fee: No