Probably some ceremonial thing like the mounds and carvings all over America.
Santa Teresinha, Brazil
Hard to drive more than a mile in my neck of the woods without seeing a mound. There's one stretch of road nearby where you can see seven mounds from one spot. A friend of mine I used to hunt arrowheads with who is now an Archeologist is working a dig site over in Chattanooga valley, over near the new VW plant. It was discovered by some construction excavation about a year and a half ago. It's apparently a burial site of chiefs or other high ranking tribe members from the woodland era. I'm told it's one of the richest finds ever in Tennessee. Lots of pristine ceremonial spears, talismans, etc.