Newark Earthworks Mounds - Ohio River Valley

Built by the Hopewell culture between 250 AD and 500 AD, the earthworks were used as places of ceremony, social gathering, trade, and worship. However, the primary purpose of the Octagon earthwork itself was scientific. The Newark Earthwork site is the largest surviving Hopewell earthwork complex in North America. The culture built many earthen mounds. Over many years, they built the single largest earthwork enclosure complex in the Ohio River Valley. The earthworks cover several square miles. Scholars have demonstrated that the Octagon Earthworks comprise a lunar observatory for tracking the moon's orbit during its 18.6-year cycle.