Hellhole

Hellhole is a large and deep pit cave in Germany Valley of eastern West Virginia. It is the seventh longest cave in the United States and is home to almost half of the world's population of Virginia big-eared bats. At 737 feet (225 m), Hellhole is the deepest of several caves in the Valley. Hellhole has had a long and storied association with the National Speleological Society dating back to the creation of that organization in the early 1940s. Many basic caving techniques (e.g, the single rope technique) were developed in Hellhole's 154-foot (47-meter) entrance drop.

Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).