Mount Diablo

From San Francisco...

Mount Diablo State Park is about 40 miles each of San Francisco. The highest point, Mount Diablo itself, is 3,849 feet high and can be seen from much of the Bay Area. There's a road to the top and you have to pay the $6 entrance fee.

From the top you get panoramic views. There is a myth that it has the second highest viewshed in the world, but thats a clearly bogus claim, in fact it was started by a property entrepreneur. It does have one of biggest viewsheds in the US. On a clear day it is possible to see Half Dome in Yosemite at about 125 miles away.

Curiously Mt Diablo is not the highest point in the Diablo Range. That honor goes to San Benito Mount at 5,241 ft .

Mt Diablo's geology is also interesting. This is its entry on the subject in Wikipedia:

"Mt. Diablo is a double pyramid and some say that it resembles a volcano (but is not). [It] is the result of geologic compression and uplift caused by the movements of the earth's plates. The mountain lies between converging earthquake faults and continues to grow slowly. While the principal faults in the region are of the slip-strike type, a significant thrust fault (with no surface trace) is found on the mountain's southwest flank. The uplift and subsequent weathering and erosion have exposed ancient oceanic Jurassic and Cretaceous age rocks that now form the summit. The mountain grows from three to five milimeters each year."