Castle Rock park resides at the base of Mount Diablo in Walnut Creek, California. It is managed by East Bay Regional Park District, which is comprised of 119,00 acres of parks land and a trail system over 1250 miles in length. Castle Rock is just one of sixty five parks in the East Bay Regional Parks District. The park itself is small being comprised of a mainly sandstone canyon and its surrounding ridges. It is bordered however by Mount Diablo State Park and Walnut Creek Open Space expanding open space access to over 18,000 acres. The Park includes Picnic areas with picnic tables, barbeques, basket-ball courts, horseshoe pits, a volley-ball pit, soft-ball field and a pool. All of the hiking trails are located outside of the picnic areas. The trails are off leash areas for dogs and are open to horses as well as mountain bikes. The park gets its name from a large rock formation with holes around the top that can be seen about a third of the way down the main canyon trail and from a number of vantage points on the opposite ridge. The rock formations in the park are a draw for rock climbers from all over the San Francisco bay area though they are only open during certain times of the year due to peregrine falcons nesting in the rocks.