Along the crest of the Santa Cruz Mountains, Castle Rock State Park embraces coast redwood, Douglas-fir, and madrone forest, most of which has been left in its wild, natural state. Steep canyons are sprinkled with unusual rock formations that are popular with rock climbers. The forest here is lush and mossy, crisscrossed by 32 miles of hiking and horseback riding trails. These trails are part of an even more extensive trail system that links the Santa Clara and San Lorenzo valleys with Castle Rock State Park, Big Basin Redwoods State Park, and the Pacific Coast.

Primitive campsites for backpackers are the only overnight facilities. Equestrians are urged to call ahead for current trail information, and smokers are advised that, due to high fire hazard, smoking is prohibited on the trails within Castle Rock State Park.