Shell ridge offers some long hot climbs, fast descents, stream crossings and little shade. There are lots of great trails to choose from here, but one route that is most popular. From the gate, follow the Briones-Mt. Diablo Trail for 4.1 miles staying on the main trail. At the Y, go left onto Wall Point. After about .5 more miles turn right up the hill. Wall Point is a good climb and will take you up to Rock City where you can find water and bathrooms. From here, turn left and climb some more for about a mile. And Turn left when you see Barbecue Terrace on your left. Find the trailhead for Pine Canyon. Strap your helmet on, because now's the time to reward yourself for the climb. Drop into the big gear and take off for 5 miles of downhill fun. Turn left onto Portugee Gap and ride this back to Briones-Mt. Diablo, turn right an go back to your car.
How to get there:
From HWY 680, take the Ygnacio Valley Rd. Exit in Walnut Creek. (From the North you need to take the Main St./Walnut Creek Exit and cross back over the freeway and continue straight until you can turn left onto Ygnacio Valley Rd.) Going East on Ygnacio, turn right onto Homestead at the bottom of the hill. Turn left again onto Marshall and follow Marshall to the park at its end.