doi.org/10.15184/aqy.2025.10237
Credibility: 989
#Peru
Hundreds of years ago, someone dedicated enormous effort to digging thousands of holes along a narrow strip atop a hill in the foothills of the Andes in southern Peru
This structure, known as Monte Sierpe, has intrigued the world since 1933, when aerial photographs taken by Robert Shippee and published by the National Geographic Society revealed the site.
Now, archaeologists believe they are closer to uncovering who built these holes and why.
A team led by archaeologist Jacob Bongers of the University of Sydney, Australia, analyzed plant material found inside the holes and suggests that the site may have initially functioned as a market and, later, as an accounting system.
“Why would ancient peoples dig more than 5,000 holes in the hills of southern Peru? Were they gardens? Did they serve to collect water or did they have some agricultural function”” Bongers asks.
“We still don’t know for sure, but new data has given us important clues and opened the way for promising theories about the site’s use.”
Mount Sierpe is an impressive feat of landscape engineering.
The strip of holes stretches for 1.5 kilometers in length and is about seven or eight holes wide, totaling approximately 5,200 holes dug into the ground, some reinforced on the sides with stones.
Building something like this required careful planning and a great deal of time, which leads to the inevitable questions: who did this and for what purpose? Theories have suggested everything from agricultural cultivation to fog harvesting.
Bongers and his team started from previous studies that proposed the site was used by the Incas as a taxation system.
They conducted extensive fieldwork, mapping the site with drones and analyzing sediment samples from the holes to identify what materials might have been deposited there and when.
Since the Inca empire arrived in the region around 1400 AD, researchers assumed that Monte Sierpe was an Inca site.
However, before the Incas, the Chincha culture had inhabited the region for centuries.
Radiocarbon dating of charcoal found in one of the pits revealed that it was deposited between 1320 and 1405 AD, suggesting that the material predates the arrival of the Incas.
Fragments of pottery found on the surface also corroborate this timeline.
This indicates that the Chincha likely built and used the site long before the Inca occupation.
The most significant discovery, according to the researchers, was the contents of the pits.
A microbotanical analysis of sediments from 19 pits revealed starch grains and corn pollen, plants from the Amaranthaceae family (which includes quinoa, spinach, beetroot, and chard), Pooidae (a subfamily of grasses that includes cereals such as oats, wheat, and barley), and Cucurbita (pumpkin).
Furthermore, plant materials such as reeds and willow species, used in basket making, were found.
These results suggest that the pits contained food plants, likely stored in baskets for transport.
“This is very intriguing,” says Bongers.
“Perhaps it was a pre-Inca market, like an open-air market.
We know that the pre-Hispanic population of the region was around 100,000 people.
It’s possible that itinerant traders, such as maritime merchants and llama caravans, as well as specialists like farmers and fishermen, gathered at the site to exchange local products, such as corn and cotton.”
Aerial images of the site revealed something not so evident from the ground: the pits are arranged in blocks that, according to the researchers, surprisingly resemble an Inca khipu, a counting device made of knotted cords, found in the same Andean valley.
This suggests that the Incas later reused the pits as a system for recording tributes, ensuring that taxes were properly collected.
“These holes can be seen as a kind of social technology that brought people together and later became a large-scale accounting system under the Inca empire,” explains Bongers.
“There are still many questions: why does this monument exist only here and not in other parts of the Andes? Could Monte Sierpe be a kind of ‘landscape khipu’? We are closer to understanding this mysterious place, and that is very exciting.”
The next step is to carry out a second phase of fieldwork to collect more samples, date other holes, and study more local khipus in order to validate and further explore these fascinating findings.
Published in 11/10/2025 06h14
Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.
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