Empire Mine State Historic Park is the site of one of the oldest, largest, deepest, longest and richest gold mines in California. The park is in Grass Valley at 10791 East Empire Street. In existence for more than 100 years, the mine produced 5.6 million ounces of gold before it closed in 1956. (5.6 million ounces of gold is equivalent to a box seven feet long, seven feet high, and seven feet deep filled with gold.) The park contains many of the mine's buildings, the owner's home and restored gardens, as well as the entrance to 367 miles (the distance, as the crow flies, from Grass Valley to Magic Mountain) of abandoned and flooded mine shafts. The park consists of forested backcountry and eight miles of trails – including easy hikes (for hiking, mountain biking and horseback riding) - in the park.