Surprisingly close to Walnut Creek, this expansive park on the slopes of Mount Diablo offers 31 miles of trails for biking, hiking and riding through oak woodlands and grasslands.
The park name derives from the marine fossils found in its limestone formations from the time when the area was covered by ocean waters. Some of these are visible at the top of the service roadnear the EBMUD water tank.
Shell Ridge connects with Borge Ranch, Castle Rocks, and Mt. Diablo State Park.