Castle Rock State Park
On Skyline Blvd in Santa Clara county
A very popular park with unique giant sandstone boulders to climb and 34 miles of hiking trails through natural wilds. The main entrance to Castle Rock is quite busy on weekends so get there early (definitely before 9:30 am) to obtain parking.
For serious backpack hikers, the famous 3-day 30-mile Skyline-To-The-Sea Trail starts in Castle Rock. For those of us who are less serious day hikers, the Skyline Trail, in Sanborn County Park just east across Highway 35 from Castle Rock’s main entrance, is a pleasant easy trail to walk or mountain bike.