Western Kentucky's Mammoth Cave is the longest cave system on Earth, with 412 miles known and mapped as of fall 2017. The name does not refer to the early discovery of fossil mastodon or mammoth bones here. Rather, the name refers to the immense size of many rooms and passages.

The old stone structure shown here is in Main Cave, the principal trunk passage in the Mammoth Cave Ridge portion of the system. In the early 1840s, an unusual underground experiment in curing tuberculosis occurred here.

Tuberculosis (TB), also called consumption, is a pulmonary disease caused by bacteria. In the early 19th century, TB patients in Europe perceived improvements in their symptoms during visits to cool, high Alpine settings or in cool cave settings. An American doctor suspected that patients might obtain relief if they spent extended periods of time in Mammoth Cave. Two stone cottages were set up in Main Cave and TB sufferers were invited to live in this area. The consumptives’ symptoms did not improve. Deaths occurred and the experiment ended after 10 months.

The patients' tents were not made of stone and no longer exist. The two stone cottages still exist and can be observed on modern cave tours (Violet City Tour and Star Chamber Tour). One of the stone structures may have been the doctor's office. Most patients' tents were nearby, but some were elsewhere (e.g., Pensacola Avenue and Audubon Avenue). Some of the deceased TB patients are buried in the old guides' cemetery near the park's visitor center.

From park signage: 1842: Doctor John Croghan used Mammoth Cave as one of the world's first hospitals devoted solely to the treatment of tuberculosis. The cave's constant temperature and humidity did not have the effect Croghan hoped, however, and the hospital closed after only 10 months.