Homestake Gold Mine, which closed in December 2001, was one of the richest gold seams ever discovered. It is located in the town of Lead, where old miners' homes cling to steep hillsides. Today, visitors can still see Open Cut, an enormous pit 550m wide, 1 500m long and 300m deep. Since 2007, the 1 100km of tunnels, caverns and underground shafts have been repurposed for use by a nuclear physics research centre.