Great Serpent Mound: Who Built It, What the Solstice Alignment Shows, and How to Visit with Respect
Who built Great Serpent Mound in Ohio, what its summer solstice alignment shows, why it sits on an impact crater, and how to visit the effigy with respect.
On a ridge above Ohio Brush Creek in Adams County, Ohio, a grass-covered earthwork winds for more than a quarter of a mile in the shape of a snake. Great Serpent Mound is the largest serpent effigy in the world and one of the most visited sacred places in the eastern United States. This guide explains what archaeologists actually know about who built it and why, what the solstice alignment shows, and how to visit well. It does not promise that the site has special energy or will change anything in you.
Contents
Great Serpent Mound is an earthen effigy of a snake near Peebles, Ohio, about 1,348 feet (411 m) long and a few feet high, with a coiled tail and an oval shape at its head. Who built it is still debated: radiocarbon dates published in 2014 point to the Adena culture around 300 BCE, while earlier dates point to the Fort Ancient culture around 1070 CE. Researchers have shown that the oval head faces the summer solstice sunset. The mound sits on an ancient meteorite impact crater. Claims that it is an energy vortex or marks a comet cannot be shown.
Great Serpent Mound in Adams County, Ohio, is an earthen snake effigy about 1,348 feet (411 m) long.
Source/tradition: Ohio History Connection, site information
Its builders are disputed: 2014 radiocarbon dates suggest Adena around 300 BCE, 1990s excavation dates suggest Fort Ancient around 1070 CE.
Source/tradition: Herrmann et al., Journal of Archaeological Science 2014; Fletcher et al., Midcontinental Journal of Archaeology 1996
The oval at the serpent's head faces the summer solstice sunset.
Source/tradition: Hardman & Hardman, Ohio Archaeologist 1987
The mound sits on a meteorite impact structure about 14 km across.
Source/tradition: Ohio Department of Natural Resources, Division of Geological Survey, 2003
The serpent embodies the great horned serpent of the waters and lower world in Eastern Woodlands mythology.
Source/tradition: Eastern Woodlands mythology as interpreted by Lepper and others
Visitors walk the path at dawn or at the solstice sunset as a contemplative practice.
Source/tradition: Contemporary visitor practice
Serpent Mound is an energy vortex or records Halley's comet of 1066.
Source/tradition: Untestable modern claims; no archaeological evidence
VERIFIED = verifiable in scientific or official sources · TRADITIONAL = historically or culturally recorded · LIVED PRACTICE = widely practiced, experiential knowledge · NOT PROVEN = spiritual interpretation, not scientifically established.
Quick answer
Great Serpent Mound is an earthen effigy of a snake near Peebles, Ohio, about 1,348 feet (411 m) long and a few feet high, with a coiled tail and an oval shape at its head. Who built it is still debated: radiocarbon dates published in 2014 point to the Adena culture around 300 BCE, while earlier dates point to the Fort Ancient culture around 1070 CE. Researchers have shown that the oval head faces the summer solstice sunset. The mound sits on an ancient meteorite impact crater. Claims that it is an energy vortex or marks a comet cannot be shown.
What Serpent Mound is
Serpent Mound is an effigy mound: an earthwork shaped like a living thing rather than a simple heap or wall. Its body rises roughly one to three feet above the ground and is some twenty feet wide, and it undulates in a series of curves along the edge of a steep bluff before ending in a tight triple coil. At the other end, the open jaws of the snake seem to hold an oval enclosure, which has been read as an egg, an eye, the sun, or a frog being swallowed.
The site also holds ordinary burial mounds from more than one period, which matters for the debate about its age. Today Serpent Mound is owned by the state and run by the Ohio History Connection, with a small museum, a paved path around the effigy and an observation tower. It is a National Historic Landmark and has been on the United States' tentative list for UNESCO World Heritage status since 2008.
For a wider view of how places like this became pilgrimage sites, see our guide to sacred places and power spots.
Who built it: Adena or Fort Ancient?
For much of the 20th century Serpent Mound was attributed to the Adena culture, which built burial mounds in the Ohio Valley between roughly 800 BCE and 100 CE, because Adena mounds lie close by. In the early 1990s a team led by Robert Fletcher and Terry Cameron excavated a small section of the serpent itself and obtained charcoal dates of around 1070 CE, which pointed instead to the Fort Ancient culture, whose people also left a burial mound on the site.
In 2014 a team including Edward Herrmann and William Monaghan published new radiocarbon dates from soil cores and argued for construction around 300 BCE, that is, Adena after all, with Fort Ancient people later repairing the effigy. The archaeologist Bradley Lepper, among others, questioned how the new samples were taken and still considers a Fort Ancient origin likely.
The honest answer is that the question is open. It is also possible that the serpent was built by one people and maintained, reshaped or reinterpreted by another over many centuries, which is how many sacred places work.
The two main dating theories
| Adena theory | Fort Ancient theory | |
|---|---|---|
| Approximate date | Around 300 BCE | Around 1070 CE |
| Key evidence | Radiocarbon from soil cores (Herrmann et al., 2014) | Charcoal from excavation of the effigy (Fletcher, Cameron et al., published 1996) |
| Main objection | Samples may be from older soil, not the build | Charcoal may come from later repair or disturbance |
| Nearby mounds | Adena burial mounds close by | Fort Ancient burial mound and village on the site |
The solstice alignment and the oval head
In 1987 Clark and Marjorie Hardman published an analysis showing that the oval at the serpent's head lines up with the direction of sunset on the summer solstice. Later researchers, including William Romain, proposed that some curves of the body point to other solar events, such as the winter solstice sunrise or the equinoxes, and possibly to lunar positions.
The summer solstice alignment is the most widely accepted and the easiest to see for yourself: stand near the head on a clear evening around June 21 and the sun sets roughly along the line of the oval. The additional alignments are more debated, because with so many curves some will point to something by chance.
Either way, an effigy that faces the longest day's sunset fits a wider pattern. Many earthworks in the Ohio Valley, from the Newark Earthworks to the octagon at High Bank, encode solar and lunar alignments with remarkable care.
Temple Tip
If you want to see the solstice alignment, check the Ohio History Connection's calendar well in advance. Seasonal events draw crowds, and the site has set hours. A quiet evening a few days before or after the solstice shows almost the same line with far fewer people.
An effigy on a crater
Serpent Mound sits on one of the most unusual geological features in the Midwest. The rocks beneath it are broken and uplifted in a circular structure about 8.7 miles (14 km) across, long called a “cryptoexplosion” structure because no one could explain it. A study by the Ohio Department of Natural Resources in 2003 confirmed that it was made by a meteorite impact hundreds of millions of years ago, identified in part by shocked quartz.
Did the builders know? Almost certainly not in geological terms. But they would have seen that the land here is strange: steep bluffs, disturbed rock and unusual formations in a small area. Some writers suggest the builders chose a place that already felt powerful. That is plausible, and it is also impossible to prove.
What the serpent may have meant
Nothing written survives from the builders, so every interpretation is an educated guess. The most careful ones draw on the mythology of Eastern Woodlands peoples recorded in later centuries, in which a great horned serpent or underwater panther rules the waters and the lower world, opposed to a thunderbird of the upper world. On that reading the serpent on its bluff above the creek belongs to the powers of water and the underworld, and the alignment to the sun ties it to the turning of the year.
Other readings see the oval as an egg and the serpent as a symbol of creation or renewal, the way snakes shed their skin, a theme explored in our guide to snake symbolism. These readings are not exclusive; a sacred image can hold many meanings at once.
What is important is humility. Serpent Mound belongs to the history of Native American peoples, and several present-day Native nations have ancestral ties to the Ohio Valley. Their perspectives on the site, where they choose to share them, carry a weight that outside theories do not.
Built, not found
It is easy to talk about Serpent Mound as a mystery. It is better to talk about it as an achievement. Moving that much earth by hand, shaping curves that still read clearly after many centuries, and aligning them to the sky required planning, skill and many people working together.
The mystery is ours, not theirs. They knew exactly what they were building.
Myths, vortexes and the comet theory
Serpent Mound has attracted more than its share of speculation. In the 19th century some writers claimed that the mound builders were a lost white race rather than Native Americans, a myth that was false and was used to justify taking Native land. Archaeology, beginning with Frederic Ward Putnam of Harvard's Peabody Museum, who excavated at the site in the late 1880s and helped buy it for preservation, put that idea to rest.
More recent claims include that the serpent maps the constellation Draco, that it records the appearance of Halley's comet in 1066, which falls close to the Fort Ancient date, and that it sits on a ley line or energy vortex. In the late 20th century the site became a gathering place for New Age celebrations. The comet idea is an interesting coincidence of dates, but there is no evidence the builders meant it; the ley line and vortex ideas cannot be tested at all.
People who visit with these ideas are welcome, of course. It is worth knowing which statements rest on evidence and which are modern beliefs laid over an ancient place, much as happened at Mount Shasta and the Lemuria legend.
Visiting Serpent Mound with respect
Serpent Mound is a sacred and a fragile place. The effigy is made of earth and can be damaged by foot traffic, so visitors walk on the paved path around it, not on the mound itself. The rules are simple: stay on the path, do not climb or sit on the mound, do not dig, and do not remove anything, not even a stone.
Many spiritually minded visitors leave offerings such as crystals, coins or tobacco. Please do not leave anything on or near the mound. Items left behind have to be removed by staff, and leaving objects at a site that is sacred to others can be experienced as disrespectful. Take your offering home and give it there, or support the site through admission and donations.
Check the Ohio History Connection website for hours, fees and seasonal events before you go, and allow time for the museum, which explains the archaeology and the geology.
Quiz: how do you want to experience Serpent Mound?
Five quick questions to find the kind of visit, or the kind of reading, that suits you.
From our shelf
Carved Crystal Snake
You cannot take the serpent home, and you should not take so much as a pebble from the mound. A small coiled snake carved from natural stone is a way to keep the memory on your desk or altar instead. Ships within 3 business days, from $18.95.
More in animal totems and crystal carvings.
Voices from practice
Visitors often describe a quiet that settles over them on the path, especially early in the morning, and many say the scale of the effigy only sinks in from the observation tower.
Staff and volunteers at sacred earthworks commonly report that the hardest part of their work is removing crystals, coins and notes left on mounds, and they ask visitors to take offerings home.
People interested in archaeoastronomy often say that seeing the solstice alignment in person is less dramatic than photographs suggest, and more moving for it: a quiet line of light across the grass.
What we don't promise
We do not promise that Serpent Mound has special energy, that it is a vortex or portal, that it will heal or change you, or that it marks any particular comet or constellation. None of this can be shown. We do not know for certain who built it or why.
What we can say is what the evidence supports: it is a carefully built effigy, it faces the summer solstice sunset, it sits on an impact crater, and it is a sacred place for many people. That is remarkable enough.
Practically: how to work with this
A respectful way to engage with Serpent Mound, whether you visit in person or from a distance:
- Read before you go. Learn the two dating theories and the solstice alignment. Knowing what is evidence and what is speculation makes the visit richer.
- Plan for the light. Choose early morning or a clear evening. For the alignment, go near June 21 and stand by the head as the sun sets.
- Walk the whole path. Start at the coiled tail and walk to the head, then climb the observation tower to see the full shape.
- Leave nothing, take nothing. No offerings on the mound, no stones in your pocket. If you want a ritual, say a few words of thanks silently or out loud on the path.
- Support the site. Pay admission, visit the museum, and consider a donation to the organization that cares for it.
- Keep the memory at home. Write about the visit, sketch the serpent, or keep a small token bought elsewhere on your altar as a reminder.
Frequently asked questions
Who built Serpent Mound?
It is debated. Radiocarbon dates published in 2014 point to the Adena culture around 300 BCE; excavation dates from the 1990s point to the Fort Ancient culture around 1070 CE. Both were Native American cultures of the Ohio Valley.
How long is Serpent Mound?
About 1,348 feet (411 meters) along its curves, making it the largest serpent effigy in the world. It rises roughly one to three feet above the ground.
Does Serpent Mound align with the solstice?
Yes. Research published by Clark and Marjorie Hardman in 1987 showed that the oval at the head faces the summer solstice sunset. Other alignments have been proposed but are more debated.
Is Serpent Mound on a meteor crater?
Yes. It sits on the Serpent Mound impact structure, about 8.7 miles (14 km) across. A 2003 Ohio Department of Natural Resources study confirmed its impact origin.
Can you walk on Serpent Mound?
No. Visitors use the paved path around the effigy to protect it. Climbing, sitting on the mound, digging and removing anything are not allowed.
Is Serpent Mound an energy vortex?
Some visitors believe so, but there is no way to measure or test such a claim. It is a modern belief, not an archaeological finding.
Sources & further reading
- Fletcher, Robert V., Terry L. Cameron, Bradley T. Lepper, Dee Anne Wymer, and William Pickard. “Serpent Mound: A Fort Ancient Icon?” Midcontinental Journal of Archaeology 21(1), 1996.
- Herrmann, Edward W., G. William Monaghan, William F. Romain, et al. “A new multistage construction chronology for the Great Serpent Mound, USA.” Journal of Archaeological Science 50, 2014.
- Hardman, Clark, and Marjorie H. Hardman. “The Great Serpent and the Sun.” Ohio Archaeologist 37(3), 1987.
- Romain, William F. Mysteries of the Hopewell: Astronomers, Geometers, and Magicians of the Eastern Woodlands. Akron: University of Akron Press, 2000.
- Ohio Department of Natural Resources, Division of Geological Survey. Serpent Mound impact structure study, 2003.
- Lepper, Bradley T. Ohio Archaeology: An Illustrated Chronicle of Ohio's Ancient American Indian Cultures. Wilmington, OH: Orange Frazer Press, 2005.
- Ohio History Connection. “Serpent Mound.” Site information, online (accessed 2026).