A National Natural Landmark under Lewisburg: one chamber a thousand feet long, three hundred wide and a hundred and twenty high, with over a mile of passage reaching 245 feet down. The War Club stalagmite stands 28 feet on its own. PUBLIC daily tours, and they run a wild-caving trip into the undeveloped sections if the walkway is not enough for you.
West Virginia
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Other places on the map within a couple of hours.