Take Ignatio Valley Road, east out of Walnut Creek. The route to the mountain is well marked.
There is something for the photographer no matter what time of year. All the views are outstanding.
An area on the slopes of Mt. Diablo is known as Rock City --- a large area of contorted, carved ancient sandstone eroded and carved by the wind. A drift of live oak leaves has been washed into a crevice by the spring rains.