When the worlds largest lead mine in Bonne Terre, MO closed down in 1963 after nearly one-hundred years of operation, the miners were understandably pissed. They left their tools and walked out. The company then shut off the pumps that kept the mine dry—and the acres of dug out caverns turned into the worlds largest underground lake. In 1992 a visionary scuba shop owner from St. Louis turned it into one of the most amazing inland dives sites in the nation. Check out time in this underworld, underwater wonderland.