Here’s what you’ll learn when you read this story:

• The famed “Band of Holes” known as Monte Sierpe in the Andes of Peru have puzzled scientists for a century.
• New research suggests the holes were the site of an ancient marketplace.
• The Inca rulers may have later used the site as a fascinating accounting system.

---

The Pisco Valley of southern Peru’s Andes Mountains features 5,200 precisely aligned ancient holes dug into the foothills. For a century, what the holes were actually used for has remained a wildly ambiguous mystery.

A team of researchers hailing from Australia to Florida think they have answer. The new theory could be one of the most unique yet, claiming the holes were part of a pre-Inca marketplace, and that the site later turned into an accounting system under Inca rule to help extract tribute.

“Why would ancient peoples make over 5,000 holes in the foothills of southern Peru? Were they gardens? Did they capture water? Did they have an agricultural function? We don’t know why they are here, but we have produced some promising new data that yield important clues and support novel theories about the site’s use,” Jacob Bongers, digital archaeologist at the University of Sydney and lead author of a new study published in the journal Antiquity, said in a statement.

The site, officially Monte Sierpe, which translates as “Serpent Mountain,” but is more commonly known as the “Band of Holes,” features roughly 5,200 aligned holes stretching nearly one mile in length, all about three-to-six-feet wide and up to three feet deep. They are dug in groupings. A 1933 aerial photograph published in National Geographic set the research community on notice, and since then hypotheses surrounding the origins have included a defense system, storage, accounting system, water collection, fog capture, and gardening.

Add marketplace to the list.

Using drones, researchers mapped the site and discovered numerical patterns in the layout of the holes. Microbotanical analysis of sediment samples show the presence of maize (corn) and ancient wild plants commonly used to make baskets, which were likely stored in the holes.

“This is very intriguing,” Bongers said. “Perhaps this was a pre-Inca marketplace, like a flea market. We know the pre-Hispanic population here was around 100,000 people. Perhaps mobile traders (seafaring merchants and llama caravans), specialists (farmers and fisherfolks), and others were coming together at the site to exchange local goods such as corn and cotton.”

That would have just been the start, though. The layout of the holes surprisingly links to the arrangement of an ancient knotted-string accounting device once used by the Inca people in the same valley.

“Fundamentally, I view these holes as a type of social technology that brought people together and later became a large-scale accounting system under the Inca Empire,” Bongers said.

Due to the terrain, getting to the site was tricky. and mapping it on the ground wasn’t productive. It was the drone technology that made it possible. “Once we had precision, low-altitude images it was immediately clear that this site was profoundly important and had to be scientifically studied,” Charles Stanish, University of South Florida researcher and senior co-author on the research, said in a statement.

Stanish said the mathematical patterning in the layout of the holes is a “spectacular find.” With archaeologists finding Inca storage sites 46 miles to the north featuring products placed on the ground in carefully crafted squares, it helps build the marketplace theory.

Positioned between two Inca administrative sites, near the intersection of a network of pre-Hispanic roads, and between the highlands and lower coast plain, the site could have served as a key gathering point.

“This is an extraordinary discovery that expands understandings about the origins and diversity of Indigenous accounting practices within and beyond the Andes,” Bongers said. “This research contributes an important Andean case study on how past communities modified landscapes to bring people together and promote interaction.”

Tim Newcomb is a journalist based in the Pacific Northwest. He covers stadiums, sneakers, gear, infrastructure, and more for a variety of publications, including Popular Mechanics. His favorite interviews have included sit-downs with Roger Federer in Switzerland, Kobe Bryant in Los Angeles, and Tinker Hatfield in Portland.