The Adena Culture emerged in the Ohio River Valley sometime between 1400 and 800 BC, and persisted until around 300 AD. Adena raised earthen mounds ranging from just a few inches to nearly 70 feet high (21 meters). Within the mounds, the honored dead were buried in sub-mound pits, log tombs, and occasionally elaborate timber structures. The human remains from the mounds were frequently found with artifacts, including copper bracelets, beads, and gorgets, as well shell, flint, and slate objects. The Adena also constructed circular earthen enclosures. These “sacred circles” usually included an interior ditch following the circuit of the earthen wall and one causewayed entryway. These structures are typically considered to have served some ritual or ceremonial purpose. The
