Jewel Cave National Monument, South Dakota: The world’s third-longest cave system has at least 195 miles of passageways, featuring fanciful and delicate formations such as gypsum flowers ...

Mammoth Cave in Kentucky is the world’s longest known cave system, with more than 400 miles ... asked the Conns to join him to explore, survey and map Jewel Cave. Deal moved away from the ...

making it the sixth-largest cave system in the world, right behind Jewel Cave in the Black Hills. “One of our explorers, she found an area, a crawl-way of a cave, in the cave, and she had no ...