Oh, the things humans will do to get their grubby hands on gold--a metal mostly prized for its ornamental use, hoarded in bank vaults and jewelry boxes, though we've arbitrarily decided it's worth, uh, its weight in gold.* The deepest gold mine in the world is Mponeng, a 2.5-mile hole in the ground in South Africa. A whole underground city--lightless and lawless--lives inside the mine.