Some residents believe that buried treasure exists somewhere in Yolo County. On October 11th of 1894, a vast quantity of gold was stolen from a Wells Fargo shipment during the The Great Yolo Train Robbery, and although some was later recovered, it is possible that the total amount was never accounted for. Details are scarce because no local newspapers existed at the time; most of what is known about the case comes from northern California newspapers, all of which were based outside the immediate area. It seems that a homeless person came across a storage of buried treasure in a nearby sand dune. The amount of gold discovered at the time did not represent the full load, and it is a mystery as to whether or not it was all eventually found, although suspects who were apprehended may have confessed the location. At the time, the missing gold was valued at $51,000, an enormous fortune for anybody who may have come across it.
It's probably easier to hunt for geocaches (which are not allowed to be buried), but it may be fun to glance around while looking in case you see some real treasures too.