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Hopewell Ceremonial Earthworks
Giant geometric earthworks in Ohio, aligned to the moon
Some 2,000 years ago, people of the Hopewell culture shaped the river valleys of southern Ohio into vast geometric enclosures of earth, perfect circles, squares and octagons spanning dozens of acres. Eight of these sites, built between about 1 and 400 CE, were inscribed together as a UNESCO World Heritage Site in 2023. They include the Newark Earthworks, the Hopewell Mound Group, Mound City, Seip and the hilltop enclosure of Fort Ancient, and five are protected within Hopewell Culture National Historical Park near Chillicothe.
The Hopewell earthworks were not towns but gathering places for ceremony, burial and exchange, filled with objects of mica, copper, shark teeth and obsidian traded from across North America. The Newark Octagon, a 50-acre enclosure joined to a circle, is aligned with the 18.6-year cycle of the moon's rising and setting points, a feat of astronomy and engineering. For more than a century a private golf course leased the Octagon, and after a long legal fight the Ohio History Connection regained full use of the site in 2025.