Star Chamber Tour A limestone and sandstone labyrinth lurks beneath the rolling hills of Kentucky’s Mammoth Cave National Park, home to the world’s largest known cave (the current surveyed distance is 400 miles, though scientists estimate the subterranean complex extends for as many as 1,000 miles). Intrepid explorers can walk through this fascinating underworld, which inspired Ralph Waldo Emerson’s transcendental appreciation of nature, on the Star Chamber Tour, a guided, evening hike.

Length 1.5 miles round-trip, 2.5 hours
Location Trail starts and ends at the Visitors’ Center
Difficulty Moderate
Highlights When the cave’s man-made lighting system shuts off for the day, hikers descend 160 feet underground to explore the passageways by lantern. You'll wander into the “hospital,” where 19th-century cave owner Dr. John Croghan treated tuberculosis patients, convinced the cool underground air was healing, and the namesake Star Chamber, which creates an illusion of the night sky.

— Molly Fergus