d) Mammoth Cave

Mammoth Cave, located in Kentucky, is the world’s largest cave system, with more than 400 miles of explored passageways. It offers a rich history and a diverse array of geological formations, including vast chambers and complex labyrinths. Mammoth Cave National Park, established to preserve the cave system, provides visitors with various tours showcasing its stunning underground landscapes. The cave’s unique ecosystem is home to a variety of wildlife, including several species of bats and cave-adapted invertebrates. Its extensive network of natural tunnels makes it a significant site for scientific study and a popular destination for tourists and caving enthusiasts.