Mount Diablo is a mountain in Contra Costa County, California in the San Francisco Bay Area, locate south of the town of Clayton and northeast of Danville. It is an isolated 3,849 feet (1,173 m) upthrust peak that is visible from most of the San Francisco Bay Area and much of northern California. Mount Diablo appears from many angles to be a double pyramid and includes many subsidiary peaks, the largest and closest of which is the other half of the double pyramid, North Peak, nearly as high in elevation at 3,557 feet (1,084 m).