The Old Borges Ranch is a 1,035 acres Historic District containing four contributing buildings, in the Diablo Foothills of the northern Diablo Range, within the 2,600-acre Walnut Creek Open Space in Contra Costa County, California. The former ranch of early Walnut Creek pioneer Frank Borges is the home base for the surrounding Shell Ridge Open Space park's activities. It is located at 1035 Castle Rock Road, south of Walnut Creek.