The Empire Mine is the site of the oldest, largest, and richest gold mine in California. From 1850 to its closing in 1956, it produced 5.8 million ounces of gold.This 5.8 million ounces of gold would fill a box 7 feet on each side. It is estimated that this represented only 20% of the available gold...80% remains. The Park contains many of the original mine buildings, the owners cottage and the restored gardens and grounds as well as the entrance to 367 miles (the equivalent of a round trip from Grass Valley to San Jose) of abandoned and flooded shafts and tunnels.