The Old Borges Ranch is a 1,035 acres (419 ha) Historic District containing four contributing buildings, in the Diablo Foothills of the northern Diablo Range, within the 2,600-acre (1,100 ha) 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.