The Empire Mine is the single best reason to visit Grass Valley, and one of the finest historic parks in California. From 1850 until its closure in 1956, this was one of the richest and deepest hard-rock gold mines in the state, and the park preserves the whole industrial complex: the shaft house, the stamp mill where ore was crushed, the mine owner's surprisingly grand Victorian "cottage," and a network of restored buildings and grounds.
The underground workings descend more than 1,500 metres below ground; visitors can peer into the main shaft and walk through mine yard buildings with interpretive exhibits. The owner's estate — built by the mining magnate William Bourn Jr. — includes a formal garden laid out in an English cottage style that feels incongruous amid the industrial machinery surrounding it. The contrast between the owners' comfort and the workers' harsh conditions is one of the park's most thought-provoking aspects. Open daily; guided tours of the cottage available weekends.