At first blush, the structures in New Mexico built by the Chacoan people and those in Ohio traced to the Hopewell culture bear little resemblance. The Chacoans, accommodating the arid desert of their home, constructed stone communal dwellings with apartments and kivas, or round gathering rooms. The Hopewellians, in their fertile midwestern fields, formed massive geometric earthworks for ceremonial or burial purposes.
But when looked at from the perspective of the sky and the cycles of the heavenly bodies, the two are more similar than they first appear. Both show a sophisticated understanding of the cosmos and a desire to acknowledge and honor its natural rhythms. And both are UNESCO World Heritage Sites because of the ancient wisdom encoded into their architecture.
Sacred Ground
Hopewell Ceremonial Earthworks encompasses eight locations across southern and central Ohio on state lands and within Hopewell Culture National Historical Park, based in Ross County, Ohio. Constructed between 100 B.C.E. and 400 C.E., the broadly scattered earthworks incorporate corresponding mathematics in features across different sites. An octagon at High Bank Works is a smaller version of the Great Octagon near Newark, Ohio, about 40 miles to the east of Columbus. A circle with the diameter of 1,054 feet repeats again and again, indicating the builders had a systematic unit of measurement. Archeologists surmise the circles were laid out with a central pole and ropes similar to a compass in geometry.
“What’s so remarkable is the same people who had this sophisticated understanding of geometry and astronomy used rather simple technology, such as clam shell hoes and baskets, to build this incredible monumental architecture,” said Brad Lepper, senior archeologist with Ohio History Connection.
Lepper said residents of the period lived in small communal homesteads and foraged, hunted, and gardened. Their epic earthwork creations reached as much as four football fields in diameter and could hold thousands of people. Research has revealed they were places of ceremony and not for everyday living. People from across the continent made pilgrimage there, bringing shark teeth from the Atlantic coast, obsidian from Yellowstone National Park, and shells from the Gulf of Mexico.
The sacred Chaco Culture sites were constructed centuries later, between 900 and 1300 C.E.., and are preserved at Chaco Culture National Historic Park and Chimney Rock National Monument in the Four Corners area. The Great House at Chimney Rock, two stories high with 35 rooms and two kivas, has many indications that it was primarily a ceremonial site, according to J. McKim Malville, professor emeritus of astrophysical and planetary sciences at University of Colorado-Boulder.
“It is on a high mesa, and in the Chaco tradition no one would have lived so high above water,” said Malville. “The presence of many ‘matates’ for grinding corn and the remains of large animals indicate it’s a place where festivals were held on a regular basis.”
Spiral Petroglyphs in Chaco Canyon that align with solstice events. (Photo courtesy of the National Park Service)
Modern Pueblos have given clues to what it might have meant to their ancestors. In Malville’s conversations with elders, they said when humans emerged from the world below, they found the surface a very dangerous place. The war gods, or “holy twins,” cleansed the Earth and made it livable. They are embodied in the two towers, close to where the Great House is.
By using dendrochronology, researchers determined that construction on the Great House coincided exactly with significant cosmological events in 1056, 1076, and 1093. Its importance also is indicated by its proximity to the two towers of Chimney Rock, which hold sacred meaning as a place where the earth and sky touch.
The Sun and the Moon
As researchers study and attempt to understand these ancient structures, one aspect has cemented their status as places of devotion: an alignment with divine cosmic rhythms.
Fajada Butte is a spectacular rock formation and one of the most sacred features of the Chaco Canyon landscape. On the winter solstice, the sun rises directly over the top when viewed from the valley floor. The juxtaposition of those two features of the earth and sky would have been obvious to the people who built structures in the canyon. Other buildings align to the winter solstice as well. Ten large domed kivas, each 60 feet in diameter and representative of the domed heavens, hosted communal religious experiences, according to Malville.
Numerous petroglyphs in the park indicate careful observation of the skies. On the summer solstice, a narrow beam, or “sun dagger,” crosses the center of a man-made spiral hidden behind three large stone slabs. On the winter solstice, two “daggers” touch the edges of the spiral. Another bug-like petroglyph captures the solar eclipse of 1097, complete with a corona.
The solar cycle is relatively well-known, and even modern people not terribly in touch with the natural world have a sense of its annual natural rhythm of light and dark. But the Hopewell earthworks and the Chaco creations also have alignments with the longer and more complex lunar cycle. Similar to the sun, the moon also has northernmost and southernmost points on the horizon – throughout its 18.6-year cycle, its setpoint swings north and south like an accordion every month, with ever increasing and decreasing angles. The cycle peaks at a major lunar standstill, when it is the furthest north in its entire range.
That standstill is framed by the two towers at Chimney Rock, and it was named a national monument because of its status as a major lunar site. It’s a phenomenon that not a lot of people see.
“I am a professor of astronomy at the University of Colorado Boulder and taught introduction classes for decades, but until I learned about Chimney Rock, I didn’t know anything about lunar standstills,” Malville said.
Significant lunar alignments are integrated into many Hopewell earthworks as well. Tracking the lunar cycle would have required generational observations. Researchers theorize the builders recorded the minimum and maximum rises and sets with stakes in the ground for decades before they encoded it in their architecture. As for the reasons why they did it, Lepper said that answer may never be known. The agricultural calendar follows the sun, so the importance of its cycle is obvious. But the lunar cycle is much longer and more complex. That, too, indicates the ceremonial nature of these places: One hypothesis is the lunar markers served as a calendar of when to gather.
Hopeton Earthworks at the Hopewell Culture NHP when significant lunar and solar alignments both happened on June 11, 2025. (Photo courtesy of Ohio History Connection)
It’s only been relatively recently that lunar alignments have been identified in those ancient structures. In fact, the ones discovered at the Octagon in Newark Earthworks surprised even the researchers. In the 1980s, Ray Hively and Robert Horn of Earlham College took a group of students on an educational trip, with the understanding that most previous researchers believed there was no lunar relationship. They first drew lines relating to the solar cycle and found no alignments in the octagon. As they plotted all eight of the lunar positions, however, they were overwhelmed that every one of them was integrated into the structure. Further research has shown elements of archaeoastronomy embedded in most of the Hopewell structures.
The sky loomed large for early Native Americans, and its cyclical changes were cause for connection, awe, and ceremony.“Archaeoastronomy highlights spectacular visual experiences with deep meaning,” Malville said. “These events are recognized around the world as powerful eruptions of the sacred into the human world.”
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