This preserve covers a large fault ridge stemming from Mt. Diablo. Shell Ridge gets its name from the abundance of fossilized shells found in the rocks along the ridge tops. The oak woodlands and savanna are teeming with wildlife. It is not uncommon for hikers to have CLOSE encounters with wild turkey, coyote, ground squirrels, woodpeckers, and various raptors. This is Walnut Creek's largest open space with about 31 miles of hiking, biking, and riding trails. While there are many access points to the open space off of Walnut Blvd. and Walnut Avenue, the main access point is located at Borges Ranch 1/2 mile past Northgate High School on Castle Rock Rd. Shell Ridge trails also offer access to several other preserves and parks including Diablo Foothills Regional Park, Castle Rock Recreation Area, and Mt. Diablo State Park. Be sure to bring plenty of water and sun protection. Map