Mammoth Cave in Kentucky is the world's largest known cave system. It's known for many things: soaring passages, ancient artifacts left behind by its first explorers and some of the most breathtaking underground scenery you could imagine. No one would expect to find a tuberculosis hospital. But for several people in the mid 1800s suffering from tuberculosis, they were willing to try anything to find a cure for an incurable disease. Even if it meant living in the depths of Mammoth Cave.