Diablo is a cyclists paradise. A short ride from Walnut Creek BART, it's far from the brutal climb and steep peak that you'd believe, when you catch a peek of it from San Francisco. Rather, Mount Diablo is a classic California landscape, rolling golden hills peppered with gnarled olive green oaks and chaparral, that gradually rises to its 3,800ft. peak. These hills, piled ever higher make the mountain-- you've got to experience it . Snaking up, through, and on the edge in switchbacks and hairpins, is the most sublime of roads, light on cars, built for bikes.
The top of Diablo is less than 20 miles from the train and a world away and the camping is generally stunning. Diablo rises far above everything around, it has one of the largest viewsheds in the Western US, and from the top you a panorama of the Bay Area, delta, and father out to the central valley and sierras (seeing Half Dome, as some would have you believe is impossible-- but no matter). There are two great campsites accessible from the north gate via Walnut Creek, Junction campground, about 3.5 miles up and 2,000' and Juniper campground 2.5 miles farther up the road at 3000'. Both have supreme views looking toward the Oakland Hills and the Bay, with Juniper offering SF city views at some sites.