Fall is coming. Let's get going.

L. L. L. Bean wants to help you make the most out of this spectacular season with gear

tips and advice for heading outdoors. For fall hikes, when it's cold in the morning and

warm in the afternoon, layering becomes very important.

You don't want to get chilled and you don't want to sweat through your clothes either.

A good rule of thumb is to start out dressed as if the temperature is 10 degrees warmer than it is.

So once you start generating body heat, you won't get overly hot.

For more tips, easy howtus, and inspiring stories, visit L.L.Bine.com.

Gide. The Kentucky countryside is dotted with rolling hills and trees, bluegrass and rivers,

but more than the natural landscape meets the eye.

With at least 5,000 caves underground,

roadside signs boast the features of this cave or that.

Broseures available at travel stops tout one cave after another.

Kentucky's most beautiful cave, a living growing cave, cave and rock shop,

underground boat cave tour, the world's longest underground swinging bridge.

So the choices are many and varied, but most people come to this region for one specific cave, mammoth cave, the longest known cave system in the world.

Over 400 miles of the cave have already been mapped, covering multiple levels, and that might be just the tip of the iceberg.

It is huge, mammoth, one might say, but in addition to its labyrinth of passageways in enormous rooms, it also holds some surprising and unique

human history.

I'm Jason Epperson and this week on America's National Parks consumption in Mammoth Cave.

Inside Mammoth Cave people notice that the air seems surprisingly fresh and that their allergies disappear like magic.

Observations like this have been noted for many years, centuries at least. the air exchange is surprisingly rapid within the cave, even at the lower depths, and the climate is naturally well controlled and consistent.

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