Over 4th of July weekend we went camping in the Eastern Sierras. The bonus was a Jeep ride to explore a deserted California mine. It's called the Chemung Mine, which may not have been gold, (possibly silver or ore) but the history is unclear so it's hard to say.
Weathered wood, bullet shells, rusty nails, tattered roofs and gigantic gears were easily accessible without any crowds or tourist centers. We took our chances walking around, which was thrilling for older kids who don't usually get to do dangerous things. I was fascinated by the 100 year old nuts and bolts holding the beams together, reflecting a century of accomplishment.