Constructed by a mysterious civilisation that left no written records, the massive site is now open to the public for the first time in more than a century.
Autumn leaves crackled under our shoes as dozens of eager tourists and I followed a guide along a grassy mound. We stopped when we reached the opening of a turf-topped circle, which was formed by another wall of mounded earth. We were at The Octagon, part of the Hopewell Ceremonial Earthworks, a large network of hand-constructed hills spread throughout central and southern Ohio that were built as many as 2,000 years ago. Indigenous people would come to The Octagon from hundreds of miles away, gathering regularly for shared rituals and worship.
“There was a sweat lodge or some kind of purification place there,” said our guide, Brad Lepper, senior archaeologist for the Ohio History Connection’s World Heritage Program (OHC), as he pointed to the circle. I looked inside to see a perfectly manicured lawn – a putting green. A tall flag marked a hole at its centre.
That’s because from 1910 through 2024, The Octagon had been used as a golf course. But on 1 January 2025, this ancient, enigmatic site reopened to visitors for the first time in more than a century.
All these prehistoric ceremonial earthworks in Ohio were created by what is now called the Hopewell Culture, a network of Native American societies that gathered from as far away as Montana and the Gulf of Mexico between roughly 100 BCE and 500 CE and were connected by a series of trade routes. Their earthworks in Ohio consist of shapes – like circles, squares and octagons – that were often connected to each other. Archaeologists are only now beginning to understand the sophistication of these engineering marvels.
Built with astonishing mathematical precision, as well as a complex astronomical alignment, these are the largest geometrical earthworks in the world that were not built as fortifications or defensive structures. And while most people have never heard about the sites or its builders, that may be about to change.
In 2023, eight of Hopewell’s earthworks were inscribed as a Unesco World Heritage site. These include The Great Circle and The Octagon in Newark, Ohio, as well Ohio’s first state park, Fort Ancient (not an actual fort). The other five are part of the Hopewell Culture National Historical Park: Mound City, Hopeton Earthworks, High Bank Works, Hopewell Mound Group and Seip Earthworks.
Lepper told me The Octagon and The Great Circle were once a larger, single Hopewell complex spanning 4.5 square miles and connected by a series of roads lined by earthwork walls. Walking through both sites today, there is an immediate shock of scale. The Great Circle, where the museum for Hopewell Ceremonial Earthworks is found, is 1,200ft in diameter. Its walls rise up to 14ft high and are outlined on the inside by a deep ditch. The Great Circle was once connected to a square and a burial ellipse, with only part of the square still visible today. The Octagon sprawls a massive 50 acres and is attached to the 20-acre Observatory Circle, a large earthwork circle for gathering and rituals connected to the observation of the night sky.
“You could put four Roman Colosseums inside just The Octagon,” Lepper told me. “Stonehenge would fit within just that small circle now serving as a putting green.” He added that 2,000 years ago, Indigenous workers built these earthworks without modern tools, digging up soil with pointed sticks and hauling it in wicker baskets on their backs. One estimate, he noted, is that they moved seven million cubic feet of dirt.
The achievement of the Hopewell Culture, however, is not simply in creating large, precise shapes, which they did without the vantage point of hills for an aerial view. They also embedded a sort of hidden geometry within these structures. Until the mounds were measured and compared, it was thought that the builders didn’t have any mathematical and geometrical sophistication, as there are no written records to testify to their level of knowledge. It was eventually discovered, however, that they made precise measurements across their earthworks and connected them in unsuspecting ways.
Lepper explained that the circumference of The Great Circle “is equal to the perimeter of the perfect square that it was connected to”, and that “the area of that perfect square is equal to the area of the [Observatory Circle] that’s connected to The Octagon”.
He added: “If you draw a square inside The Octagon by drawing a line from alternate corners of The Octagon, the sides of that square [1,054ft] are equal to the diameter of the circle that it’s attached to [1,054ft].”
Examples of this interplay between earthworks have been found repeatedly by archaeologists. According to Lepper, that measure of 1054ft, whether halved or doubled, is found in other Indigenous earthworks across the country, and served as a common unit of measure.
While the Hopewell Culture’s geometrical and mathematical knowledge astonished scholars, another level of sophistication appears when the layers are peeled back further: astronomical alignment.
In the 1980s, two professors at Earlham College in Indiana, Ray Hively (a physicist and astronomer) and Robert Horn (a philosopher), decided to pay a visit to The Octagon and its attached Observatory Circle. As astronomical monuments like Stonehenge had received great attention, they wondered if these earthworks were also aligned to a solar calendar.
Hively and Horn found no solar connections, but they then considered an alternative purpose: the lunar cycle.
“We thought deliberate lunar alignments unlikely at Newark,” they wrote, because while the Sun can be tracked over a year, a complete lunar cycle takes 18.6 years. Even so, the lunar cycle proved to correspond to the position of the Observatory Mound at The Observatory Circle. There, one can watch the Moon rise over the exact centre of The Octagon in the distance every 18.6 years.
“Astronomical alignments are only relevant and useful if they somehow tie the celestial orbs to belief systems and understandings of life,” said Timothy Darvill, professor of archaeology at Bournemouth University who has researched both Stonehenge and the Hopewell Ceremonial Earthworks. “The ceremonies around the observation of the skyscape could well have a secondary function in terms of fostering community.”
That ancient community and culture was part of the reason for its Unesco World Heritage Site inclusion.
A Unesco site needs to show that it has “outstanding universal value”, said Jennifer Aultman, director of historic sites and museums at Ohio History Connection which helped lead its Unesco consideration. One criterion for this, she said, “is that these are masterpieces of human creative genius”, which is where these mathematical, geometrical and astronomical features are important. The other, “is that they bear really exceptional testimony to the cultural tradition that produced them”.
Aultman explained: “You really can understand something about the lives of the people and what mattered to them by looking at, and learning about, the earthworks.”
Consider the Moon, for example, which was clearly important for the Hopewell Culture. Darvill told me that, for some cultures, the “Sun, Moon… are considered to have power over what happens on a day-to-day basis. As such, the heavenly bodies are often deified, which is how their power is justified and rationalised.” It is therefore likely that the Moon was a deity shared by those who gathered at the mounds.
“The land we know as Ohio is home to a number of extraordinary earthworks built by Indigenous residents of this region thousands of years ago,” said Megan Wood, executive director and CEO of the Ohio History Connection. While not all earthworks in Ohio are specifically Hopewell Mounds – such as the solar-aligned Serpent Mound Historical Site in Peebles, Ohio, for example – Wood sees them all as “icons” of Indigenous “cultural achievements”.
Since the Hopewell Culture left no written records, only the earthworks and the few objects retrieved from them serve as their last cultural testimony. While archaeological excavations continue on some sites, objects like ritual smoking pipes and a small stone statue of a shaman wearing a bear skin and holding a human skull called “the Shaman of Newark” have been found. As these earthworks were gathering places and not villages, artefacts representing the locations from where these Indigenous peoples travelled have also been discovered, like effigy pipes, a copper head plate and an obsidian knife.
However, after the Hopewell Culture gradually began to disappear starting around 500 CE, other Indigenous peoples stepped in to become caretakers of the land. One of those groups was the Shawnee Tribe, which called Ohio home before they were forcibly removed west of the Mississippi River in the 1830s.
“We may not have been responsible for building or creating them, but I know that my ancestors lived there, and that my ancestors protected them and respected them,” said Chief Glenna Wallace of the Eastern Shawnee Tribe of Oklahoma, who believes that other tribes should have a role in the future of protecting the Hopewell Earthworks and communicating their cultural importance.
For years, The Octagon was under the control of the Moundbuilders Country Club. After more than a decade of negotiations, the OHC and the club finally reached a deal in 2024 to transfer the site’s long-term lease to the historical society, paving the way for them to open the earthworks to visitors beginning this January.
Source : https://www.bbc.com/travel/article/20221204-the-us-2000-year-old-mystery-mounds
