We’ve learned a lot about medicine over the years, and treatments that once seemed perfectly logical—ingesting mercury, for example—are now completely laughable.

Take Dr. John Croghan, whose specialty was "pulmonary consumption," now known as tuberculosis. Croghan had read that interesting things were happening in Mammoth Cave in Central Kentucky: Nothing there seemed to decay. Not fallen trees, not dead bats, not even the corpses of Native Americans that had been found within the depths of the cave. Croghan concluded there must be something special about the air within the cave, and purchased the 2000 acres of land that contained it. If it could keep the dead from rotting, the doctor figured, then it might just be able to stop TB in its tracks.

At first, it seemed as though the patients who moved into huts in the cave were seeing vast improvement. Croghan was elated and began planning a hotel in one of the larger rooms, sure that patients would soon flock from all over the world to experience the restorative wonder of Mammoth Cave.

Signatures written in smoke on the roof of the cave. (Stacy Conradt)

But Pet Sematary it was not. Even if the air did have some sort of magic power, the cool air combined with the smoke that gathered from the patients’ oil-burning lamps and campfires definitely did more harm to battered lungs than good. In a matter of months, Croghan had five dead patients on his hands, and he had to admit that the Mammoth Cave Tuberculosis Ward was not the miracle cure he thought it was. In fact, Croghan himself succumbed to the disease in 1849.

You won’t find any patients in the caves these days, but two of the stone huts from the failed experiment still remain. You can see them if you take Mammoth Cave’s Violet City tour, a three-hour trek lit only by lanterns. It’s said that if you listen hard enough, you can still hear coughing.