Grab your flashlight and lace up your hiking boots for a visit to a fantastic unchartered universe— the world of caves. Deep inside Kentucky's "Underground Everest," the world's longest cave, explore miles of passages and discover fossil remains of humans who braved the darkness up to 3,000 years ago. Visit an ice cave in the Austrian Alps and climb down a quarter-mile underground in New Mexico's Lechuguilla. Marvel at breathtaking mineral formations and a kingdom of bats that use their ears to guide them— just a few of the many wonders in Mysteries Underground.