For additional details on the Lost City, see the Lost City of Volvon geocache.
There are at least three mortar holes at the site. But there is no doubt why this particular spot was a Volvon camp site -- it has an absolutely magnificent view of the valley in the foreground and Mt. Diablo in the background. If this were a modern homesite, it surely would have a big premium for its view. Here is a photo: PHOTO.
Some other close-by mortar hole sites are: N37 50.121 W121 47.975 and N37 50.077 W121 47.974.
A trail to the cache site starts from the Volvon Trail at N37 50.253 W121 47.829. You can also reach the cache site by hiking uphill (partly cross-country) from the intersection of the Stone Corral Trail and the Coyote Trail at N37 50.202 W121 48.247. There is some poison oak and stickers at the site, so be careful.
Come and enjoy this great site, but PLEASE DO NOT DISTURB, HARM OR REMOVE any Native American items, as they are strictly protected by federal and state laws.