The Newark Earthworks were the largest set of geometric earthen enclosures in the world. Built by prehistoric Hopewell people between 100 BC and AD 500, the architectural wonder was part cathedral, part cemetery, and part astronomical observatory. Three segments of the structures have been preserved, including Great Circle Earthworks formerly known as Moundbuilders State Memorial), Octagon Earthworks, and Wright Earthworks. The three offer the best-preserved examples of the monumental geometric earthworks of the Hopewell culture. Visitors can stop in to The Great Circle Museum to watch an interactive video explaining the significance of the site and tour a 1,000-square-foot exhibit that includes a timeline of Ohio's ancient cultures and an explanation explaining how earlier residents of the state saw the Newark Earthworks as a sacred site, and how the earthworks align with the rising and setting of the moon. Group tours can be scheduled in advance by calling the office.