Castle Rocks State Park Picnic Area is reserved for large, organized groups, such as clubs and office parties. There are hiking trails that bypass the picnic area and lead to a large canyon carved into the side of Mt. Diablo.
Of particular interest in this canyon is Castle Rocks, an area where beds of sandstone have been tilted almost 90 degrees so that they are now almost vertical. These monoliths are nesting sites for raptors in the spring, and during this time the area is posted against human intrusion. At other times this is a favorite rock climbing site. It is also possible to hike among the monoliths without having to rock climb, but one must be cautious and it is best to go with an experienced guide.
In the wet season you may have to wade across the creek at several crossings.
Another way to get to the rocks is to hike south from Borges Ranch and hike down into the canyon on the fire road. For pictures of Castle Rocks, see the Borges Ranch Hiking Page.
To get to the trailhead take Oak grove south past the Mt.Diablo turnoff at Northgate Road. Continue past the Borges Ranch turnoff. The road will end at the ranch buildings after passing a large staging and picnic area
See also [Wildland Hiking Precautions]