Martin Ridge Cave System
The Whigpistle Cave System is a large cave near Mammoth Cave, in the U.S. state of Kentucky. The system, composed of the interconnected Whigpistle, Martin Ridge, and Jackpot Caves, has been mapped to over 66 kilometers (41 mi), and is currently the United States' thirteenth-longest cave.
Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).