01
Sep
1. Mammoth Cave, KentuckyMammoth Cave National Park is home to the longest known cave system in the world, with more than 420 miles of surveyed passageways and ongoing discoveries each year. Designated a UNESCO World Heritage Site and International Biosphere Reserve, it offers a vast labyrinth of limestone corridors formed over millions of years by the Green River.Visitors can explore features such as the Rotunda, one of the largest cave rooms in the eastern United States, and Frozen Niagara, a stunning flowstone formation. Guided tours range from easy walking routes to challenging lantern-lit excursions that highlight the cave’s historical use…
