Zip lining in a cave? Yes, MEGA ZIPS in Louisville, Kentucky is the only underground zipline and adventure tour in the world! This is a man-made cavern that was a former limestone mine converted to an underground adventure park with 6 zip lines (including a dual racing zip!) and 2 challenge bridges. The up to 2 hour tour will have you jumping off of 70 foot platforms and zipping through darkened caverns with ceiling heights of 90 feet. Fun and scary!