A hot afternoon in July, under deep blue skies, I made time to visit the Empire Mine State Park near Grass Valley. The largest, deepest, and richest gold mine in California, operating from 1850 to 1956, this hard-rock mine extracted 5.8 million ounces of gold from deep underground, and the history, buildings, and equipment have been preserved in a museum.

It is picturesque, but also frightening. Men worked under unbelievable conditions, shuttled down in skiffs as much a mile below ground, through 367 miles of nearly airless and lightless tunnels.

On a quiet afternoon, with hardly anyone there, it was possible to clearly conjure these gold-rushed lives, the brutality of the conditions, the extraordinary courage of the men, the grit and clamor and claustrophobia. There is a haunting silence in the motionless machinery that still resides in the buildings, locked in dust and rust.

With the prosperity generated, the mine owners built intricate and beautiful "cottages", gardens and fountains, which have been meticulously maintained.