We visited Ocmulgee National Monument on our way out of Macon. It’s a Native American site (Muskogee) with a good little museum and several mounds – you can go into the Earth Lodge which has the genuine floor, about 1100 years old, but reconstructed walls. As in Maes Howe in Orkney, it is aligned so that on certain days the sun shines directly through the entrance tunnel across the centre.
The other mounds were used as temples (one was partially destroyed during the construction of a railroad) and for funerals. Eventually the Muskogee were displaced and ended up in Oklahoma. The usual sad and shameful story.