Castle Rock Park is a regional park part of the East Bay Regional Park District

East Bay Regional Park District

The East Bay Regional Park District is a special district operating in Alameda County and Contra Costa County, California, within the East Bay area of the San Francisco Bay Area...

. The park lies in a scenic sandstone canyon

Canyon

A canyon or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of...

 close to Mount Diablo in the Diablo Foothills. The park is bordered by Mount Diablo State Park

Mount Diablo State Park

Mount Diablo is a mountain in Contra Costa County, California in the San Francisco Bay Area, located south of Clayton and northeast of Danville. It is an isolated upthrust peak of , visible from most of the San Francisco Bay Area and much of northern California...

 and Walnut Creek Open Space; together, these three parks provide 18000 acres (72.8 km²) of parkland for visitors to enjoy.

Castle Rock Park should not be confused with Castle Rock State Park

Castle Rock State Park (California)

Castle Rock State Park is a state park of California, USA, located along the crest of the Santa Cruz Mountains. It 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 is a...

, which is a state park located across the San Francisco Bay

San Francisco Bay

San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...

 in the Santa Cruz Mountains

Santa Cruz Mountains

The Santa Cruz Mountains, part of the Pacific Coast Ranges, are a mountain range in central California, United States. They form a ridge along the San Francisco Peninsula, south of San Francisco, separating the Pacific Ocean from San Francisco Bay and the Santa Clara Valley, and continuing south,...

 between Saratoga

Saratoga, California

Saratoga is a city in Santa Clara County, California, USA. It is located on the west side of the Santa Clara Valley, directly west of San Jose, in the San Francisco Bay area. The population was 29,926 at the 2010 census....

 and Boulder Creek

Boulder Creek, California

Boulder Creek is a census-designated place in Santa Cruz County, California, United States. The population was 4,923 at the 2010 census.-Geography:Boulder Creek is located at ....

.