In the foothills of southern Peru, roughly 20 miles east of Pisco, the ground is pockmarked with over 5,200 deliberate holes arranged in a precise grid. For nearly a century, the Band of Holes—also called Monte Sierpe—has puzzled archaeologists. Some outsiders blamed ancient astronauts. Others guessed they were for defense, gardening, or water collection. Now, new research suggests a more grounded answer: they were a marketplace, then a ledger.
The holes—each between three and six feet wide and up to three feet deep—were discovered in 1931 during an aerial survey, then largely forgotten. This November, archaeologists published findings in Antiquity that finally piece together their purpose. The holes were dug roughly 1,000 years ago by the Chincha people, who used them as a gathering place to exchange food and goods. Four centuries later, when the Inca Empire conquered the region, they repurposed the same site as an accounting system to track tributes from local groups.
Researchers arrived at this conclusion by studying sediment samples and drone imagery. The pollen analysis revealed traces of at least 27 plants—maize, sweet potato, and bulrush grass used to weave baskets. The presence of these materials suggests humans deliberately transported goods to the site, likely placing them in the holes as part of a barter system. "Large numbers of people depositing goods in the holes could have been a way of publicly displaying information about the quantity of goods available, as well as the quantity of goods required for a fair exchange," explains Jacob Bongers, an archaeologist at the University of Sydney who led the study. A certain number of holes filled with maize might have equaled a certain number with cotton or coca—a transparent, standardized exchange.
We're a new kind of news feed.
Regular news is designed to drain you. We're a non-profit built to restore you. Every story we publish is scored for impact, progress, and hope.
Start Your News DetoxA System of Order
The overhead imagery revealed something striking: the snaking formation of 5,200 holes contains more than 60 sections separated by strips of land, with varying numbers of rows in each block. Some sections hold multiple rows of eight holes; others alternate between eight, seven, eight, seven. "There are these interesting mathematical patterns," Bongers notes. "It hints that there was some sort of intention behind it."
This deliberate arrangement reminded researchers of quipus—Inca record-keeping devices made from knotted cords used to track everything from census data to tribute records. The Band of Holes, arranged in a similar logical structure, likely served the same purpose under Inca rule. The site's location strengthens this theory: it sits between two Inca administrative centers, at the intersection of pre-Hispanic roads, in a transitional ecological zone where different ethnic groups would naturally gather to trade.
Not all archaeologists are convinced. Karenleigh Overmann, at the University of Colorado Colorado Springs, points out that the Inca used a decimal system—if the holes were truly an accounting device, they'd likely be grouped in tens, not eights. The debate continues, but what's clear is that the Band of Holes was no accident. For at least 600 years, it served as a hub where communities met, exchanged, and kept records—a physical marketplace that became a physical ledger.
