For additional details on the Lost City, see the Lost City of Volvon geocache.
The Volvon mortars are not exactly at the cache coordinates (they are too close to another geocache), but are approximately 40 meters (120 feet) to the west, in the trees at the western edge of the lovely meadow: There are some particularly striking mortar holes at N37 49.513 W121 47.579. By one count, there are 46 holes in the meadow area.
Note that there is some poison oak in the cache area -- 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.