Fort Ancient: Two Thousand Years of Sacred Geometry

Just east of Interstate Seventy-One, above a bend in the Little Miami River in Warren County, a three-and-a-half-mile wall of earth curves across a hilltop in ways that have puzzled and astonished observers for two centuries. This is Fort Ancient, one of the largest and most complex prehistoric earthworks in North America, and as of September of two thousand twenty-three, a UNESCO World Heritage Site.

The walls were not built by any culture that Europeans encountered. They were raised by the Hopewell people, a remarkably widespread network of Native American societies whose ceremonial world stretched from the Gulf Coast to the Great Lakes between roughly one hundred years before the common era and two hundred ninety years after it. That is nearly four hundred years of construction, spanning at least nineteen generations of builders who shaped more than eighteen thousand tons of earth into precise enclosures.

The three major sections of the earthwork enclose the hilltop in a shape that archaeologists now believe was not accidental. Recent research has found that walls and openings align with key positions of the sun and the moon, including the far more complex eighteen-and-a-half-year lunar standstill cycle. Fort Ancient, in other words, may be a landscape-scale astronomical calendar, a living instrument for tracking the movements of the heavens across generations.

The Hopewell people who built it also farmed corn, beans, and squash along the Little Miami below, and maintained a village inside the southern enclosure. When European settlers arrived they assumed the earthworks were a fort, hence the name, but there is no evidence of military use. The walls have no defensive angles, no evidence of warfare, only ceremony.

In two thousand twenty-three, Fort Ancient was inscribed alongside seven other Ohio earthwork sites as part of the Hopewell Ceremonial Earthworks, becoming the twenty-fifth UNESCO World Heritage Site in the United States and the first in Ohio's history. The place that settlers called a fort turns out to have been a temple.