Untold Earth | This Upside Down Cave Is a Microscopic Warzone | Season 1 | Episode 9 | PBS

Below the Chihuahuan Desert in southeastern New Mexico, lies an extensive system of limestone caves, among them the famed Carlsbad Cavern, home to one of North America's largest underground chambers. But there is more to this subterranean world than gigantic geological formations. It is also ground zero for a microbial war that’s been raging for thousands of years, right beneath our feet.