The Lost Sea

Under Sweetwater, Tennessee is the largest underground lake in the United States, more than a hectare of water in a cave and still not fully mapped, with divers finding more rooms beyond every explored edge. The cave was used as a Confederate saltpetre works and later, less respectably, as a speakeasy and a cockfighting pit. Pleistocene jaguar tracks and bones were found in the upper passages. You tour it by boat over water that is deep, clear and full of trout. PUBLIC show cave, guided only.