The I've spent the last 25 years as a ranger at the Wind Cave National Park here in western South Dakota.

Teddy Roosevelt established the place back in the early 1900s, and it's one of the first six national parks ever founded.

But although it's more than 50 square miles of dense forests, mixed grass, prairie, and rocky hills,

it takes its name from the geological phenomenon that is Wind Cave.

Wind Cave is the largest of its kind in the entire world,

and has more passage volume per cubic mile than any other on the planet,

which, in plain English, means there are more underground tunnels under the park than any other on the planet, which in plain English means there are more underground

tunnels under the park than any other place in the world.

On top of that, only around 10% of them have been fully explored, meaning there are thousands

of miles of unexplored passageways, and at the going rate, technology permitting, of course,

it'll take scientists and cavers more than 600 years to fully explore them. The Lakota Native Americans who made the area their

home spoke of a living, breathing cave system through which their ancestors had crawled from the

underworld during the first days of creation.

They called the caves Washanaya, and they played an important role in the culture and creation myths of their people, who speak of Tokahe, or the first man emerging from the darkness.

It sounds like classical, mythological storytelling, yet the Lakota's belief that wind cave is a living,

breathing network of tunnels is not entirely unfounded.

When high pressure is higher outside the cave than inside it, air flows into the cave,

raising the cave's internal pressure to match outside pressure.

The process also works in the exact opposite way, meaning that in some of the larger caves,

the continuous flow of air really does give the impression that the earth itself is inhaling

and exhaling.

As you can imagine, such an incredible natural phenomenon attracts a lot of visitors each year, and for the most part,

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