I found it interesting. It's thought to be a burial mound... so its never been excavated? Or they aren't talking. Hmmm
I visited serpent mound in Ohio a couple years ago. It's been recently discovered that the head of the serpent sits on the edge of a meteor crater, and its body aligns with the equinox in the spring and fall. There are many astrological facts associated with it, and its believed there are more to be discovered.