Etowah Indian Mounds, Bartow County, Georgia, USA.

Shown in the second photo is a reconstruction of what the site would have looked like during its apex. 

The Etowah site has produced some extraordinary Mississippian artifacts and includes one of the largest platform mounds ever built in North America. The fifty-acre site once contained six mounds, the three largest of which still remain, and two plazas surrounded by a large moat and an impressive bastioned stockade.

The site was home to at least 3 separate chiefdoms during the approximately 600-year span of the Mississippian period.

[…] Hernando de Soto and his army visited Etowah, known to the Spanish as Itaba, in 1541. At the time, it was no longer the seat of regional power, but merely the home of a subchief under the direct influence of the chief of Coosa, whose capital was located nearby.

-Eric E. Bowne in Mound Sites of the Ancient South: A Guide to the Mississippian Chiefdoms (2013), page 147.

Photos taken by Kevin TrotmanMuora, & Heironymous Rowe. I would also highly recommend Bowne’s cited publication for further reading on the site.