The world’s longest cave sys­tem and a UNESCO World Her­itage Site. Mam­moth Cave was estab­lished as a nation­al park on July 1, 1941 although peo­ple have been tour­ing the caves since the 1800’s. Cur­rent­ly, over 400 miles of the cave sys­tem have been explored and mapped, with new dis­cov­er­ies being made all of the time. Bats dwell inside of the cave. Karst cave sys­tem. The cave was formed in a lay­er of lime­stone under the Flint Range in the west­ern foothills of the Appalachi­ans. The length of the explored part of the cave sys­tem is 676 km. In the sur­veyed part there are 225 under­ground pas­sages, about 20 large halls and more than 20 deep shafts. Depth — 115 m. The cave was dis­cov­ered by Amer­i­can pio­neers in 1797.