You really can step back into time at Gold Bug Park & Mine in Placerville (CA). The hard-rock gold mine offers a chance to walk over 300′ into a drift (a mining term meaning a horizontal passageway) with hard-hats. It is a self-guided audio tour through the mine. Admission also includes entrance to the Hendy Stamp Mill where a working scale model demonstrates the ore reduction process. The park also includes a picnic area, gift shop and museum. Admission is $5 for adults. You can pan for gems for a small fee.
For more information visit: http://www.goldbugpark.org/