Mt. Diablo, located in the SF East Bay, is the place that all of Northern and Central California & all of Nevada were mapped. The summit - 3,849' - offers a sweeping panorama--more of the earth's surface can be seen from the mountain than any other peak in the world, except Mt. Kilimanjaro in Africa.
Here is a link to more info:
http://www.savemountdiablo.org/AboutMountDiablo.htm