At 3,849 feet, Mt. Diablo is not that high, but its location makes its viewshed spectacular. On a clear day you can see the Sierra Nevada, Yosemite's Sentinel Ridge, all 8 bridges on the SF bay and Mt. Lassen from the visitor center at the top. This is shot from the east side (Sac River Delta).
Diablo from the East by
lennycarl08, on Flickr