For decades, archaeologists have puzzled over thousands of peculiar depressions scattered across the landscape of southern Peru. Known as the “Band of Holes,” the formation consists of a long, narrow grid of uniformly dug cavities that appear deliberate and highly organized. While some observers have suggested fantastical theories—such as handiwork by “ancient astronauts”—others have proposed more practical explanations involving defense, irrigation, or water collection.
A new study published on November 10 in Antiquity offers a fresh interpretation. According to the researchers, the holes were likely created about 1,000 years ago by the Chincha people as a centralized gathering place for exchanging goods and food. When the Inca Empire conquered the region roughly four centuries later, they may have repurposed the site as a collection point for tribute from local communities.
Located around 20 miles east of Pisco in the Andean foothills, the Band of Holes—also called Monte Sierpe—stretches nearly a mile and contains approximately 5,200 holes, each measuring three to six feet across and up to three feet deep. The formation was first documented in 1931 by geologist Robert Shippee and Navy Lieutenant George R. Johnson during an aerial photography survey. Their striking images, later published by National Geographic, brought widespread attention to the mysterious site.
To investigate further, the research team collected sediment samples and captured high-resolution drone images. The samples revealed pollen from at least 27 plant species, including maize, sweet potatoes, and bulrush—a wild grass used by the Chincha to weave baskets. Because wind dispersal is unlikely to explain the pollen concentration, researchers believe the plants were carried to the site by people.
They propose that local groups may have lined the holes with plant material before placing goods inside them. Baskets made from bulrush may have been used to transport items to this communal exchange hub. According to lead author Jacob Bongers of the University of Sydney, the filled holes may have served as a visual display of available goods and needs—an early form of market transparency. For instance, a certain number of holes filled with maize might have represented an equivalent value to holes filled with cotton or coca.
Drone imagery also revealed that the Band of Holes is divided into more than 60 sections separated by strips of untouched land. These blocks contain varying numbers of rows and different counts of holes. Some segments have repeated patterns—such as alternating rows of eight and seven—that suggest intentional design.
This patterning reminded the researchers of quipus, the knotted-cord devices the Inca used for accounting and record-keeping. They hypothesize that after the Inca takeover, the site may have served as a large-scale tribute-measuring device. The location supports this idea: the Band of Holes sits between two Inca administrative centers and lies at a crossroads of pre-Hispanic travel routes within a transitional ecological zone known as a chaupiyunga.
“This was a key meeting point between valley and highland groups,” says anthropologist Jordan Dalton, who was not involved in the study. “It makes this interpretation particularly compelling.”
Still, not all scholars are persuaded. Archaeologist Karenleigh Overmann argues that if the depressions functioned as an Inca accounting system, they would likely be organized in decimal-based groups, consistent with Inca numerical practices. She also notes that the nearby quipu contains 80 sections, whereas the Band of Holes has only 60.
Overmann suggests an alternative: the formation may simply be a massive geoglyph, part of a tradition of large-scale, visually striking designs in Peru. The authors acknowledge this possibility as well but propose that the site could have served multiple functions.
Bongers sees the Band of Holes as a “social technology”—a monumental signal visible from miles away that helped coordinate gatherings long before the era of digital communication. “Without the internet or cellphones,” he says, “people still needed ways to determine where and when to meet. This site may have fulfilled that purpose.”
