Mammoth Cave, located in Kentucky, is the world's longest known cave system.

Mammoth Cave, a UNESCO World Heritage Site, is located in the Appalachian region of Kentucky and is renowned for being the longest known cave system in the world, with over 400 miles of explored passageways. The cave is famous for its unique geological formations, underground rivers, and diverse ecosystems. It attracts visitors for guided tours, where they can explore various sections of the cave and learn about its history and natural features.