"We are making our way up the Natchez Trace Parkway from Natchez, Mississippi to Nashville, Tennessee, and today we are very near the Mississippi-Alabama State line at an exhibit called Cave Spring.

"The basic type of rock in this area is limestone. When rain falls, the water absorbs carbon dioxide from the air and this forms a weak acid. As this water seeps through the ground it dissolves the limestone very slowly. At this site, the underground water dissolved a large cavern out of the limestone just beneath the surface and eventually the roof of the cavern gave way and the ground here fell in to open up a cavern filled with spring water. This spring was probably used as a source of water by the Indians in this area over the millennia; however, today the spring water is unsafe to drink and the cavern is dangerous, so visitors to the Cave Spring exhibit are cautioned to be careful -- look but don't touch.

"There is another exhibit near Cave Spring, actually just a few tenths of a mile to the north. It's the last exhibit within the State of Mississippi and is the oldest site on the entire Natchez Trace. So, join us on our next program when we will visit the Bear Creek Mound. For Natchez Trace a road through the wilderness, I'm Frank Thomas."

For more about Natchez Trace: A Road Through the Wilderness, visit eddieandfrank.com