This small hole leads into an underground labyrinth that ties into Mammoth Cave National Park/Bill Stringfellow via the Southeastern Cave Conservancy

It's pretty obscure, little more than the mouth of a bear den, but it leads into a fascinating underworld and ties into the world's longest cave that is protected by Mammoth Cave National Park in Kentucky.

And thanks to the Southeastern Cave Conservancy, Inc., the Daleo Entrance to Mammoth Cave that is just about a mile east of the national park is being protected by the nonprofit organization.

The land surrounding the entrance, now named the Elroy and Marilyn Daleo Cave Preserve, protects 88 acres of classic karst on the Mammoth Cave Plateau. It recently was purchased by the cave conservancy.

The Daleo Entrance is the only entrance to Mammoth Cave outside the national park owned by a conservation organization. The preserve includes a number of caves, most notably the Daleo Entrance to the Roppel section of Mammoth Cave. The Daleo entrance is a significant portal into much of the cave system, and its acquisition is important in the overall goal of protecting the unique resources of the longest cave on Earth. 

The "Western Kentucky Parkway" section of the cave shown here is the principal transport conduit that carries flood water across the two large drainage basins that the cave spans/Ann and Peter Bosted via the Southeastern Cave Conservancy

Those interested in supporting the Elroy and Marilyn Daleo Cave Preserve acquisition and stewardship, can do so at this site. Founded in 1991, SCCi is the world’s largest land conservancy dedicated solely to cave conservation. SCCi conserves some of the Southeast’s most significant wild caves, while protecting the habitat of many endangered animals, preserving historic artifacts, and providing some of the best recreational caving anywhere.