The Band of Holes on Monte Sierpe in southern Peru includes over 5,000 pits running nearly a mile. New drone-based mapping and sediment analysis reveal at least 60 grouped sections with repeating numerical patterns that researchers compare to Inca khipus — knotted-cord accounting devices. The site was likely active c.1400–1532 and lies between two Inca administrative centers, suggesting a role in tribute or redistribution, though pollen evidence also supports an earlier Chincha barter function. Authors call the tax-ledger interpretation tentative but increasingly plausible.
Could Peru’s 'Band of Holes' Be an Inca Tax Ledger? New Study Points to Public Accounting
The Band of Holes on Monte Sierpe in southern Peru includes over 5,000 pits running nearly a mile. New drone-based mapping and sediment analysis reveal at least 60 grouped sections with repeating numerical patterns that researchers compare to Inca khipus — knotted-cord accounting devices. The site was likely active c.1400–1532 and lies between two Inca administrative centers, suggesting a role in tribute or redistribution, though pollen evidence also supports an earlier Chincha barter function. Authors call the tax-ledger interpretation tentative but increasingly plausible.
06:33 AM, 11/11/2025Culture
Could the Band of Holes on Monte Sierpe have been an Inca record-keeping system?
On Monte Sierpe in southern Peru — nicknamed “serpent mountain” — more than 5,000 carefully arranged pits run in lines for nearly a mile. First photographed from the air by National Geographic explorer Robert Shippee in 1933, this so-called "Band of Holes" has inspired many explanations, from water-catchment or agricultural features to ritual uses and even extraterrestrial speculation.
New analysis and context
A recent international study published in the journal Antiquity used drone imagery, mapping and sediment analysis to identify precise and repeating patterns across the site. The authors report the pits are grouped into at least 60 discrete blocks, with numerical regularities within those blocks — for example, alternating repetitions in how many holes appear in each row.
Why researchers think it may be administrative
The feature appears to have been used continuously between roughly 1400 and 1532 and lies near former pre-Hispanic trade corridors, midway between the Inca administrative centers of Tambo Colorado and Lima La Vieja. Those factors, the authors argue, strengthen the idea that the site related to administration, trade or redistribution.
Scholars compare the layout to khipus — knotted-cord recording devices used by the Inca to tally census information, tribute and other data. More than 1,000 surviving khipus have been identified by researchers, and one khipu found near Monte Sierpe is organized into 80 cord groups, a structure the paper’s authors say resembles the band of pits in its grouped organization.
“The regularity of these squares is comparable to the numerical patterns at Monte Sierpe, suggesting a potentially similar purpose: the counting and sorting of different goods,” the authors write.
Alternate and earlier uses
The authors are cautious and note the site may not have originated as an Inca tax ledger. Sediment samples from pits contained ancient pollen from willow — traditionally used for baskets and mats — and from maize. These findings support a hypothesis that the earlier Chincha Kingdom might have used the pits as a standardized system for barter or public displays of commodity quantities: filling a set number of pits with one good to indicate its exchange value relative to another.
What this means
Rather than a single definitive explanation, the study offers a nuanced view: the pits may have been adapted over time, first serving local economic or display functions under the Chincha and later repurposed within Inca administrative systems for tribute and redistribution.
The authors, including Jacob Bongers and Charles Stanish, describe their interpretations as tentative but say the new evidence brings researchers closer to understanding one of the most enigmatic archaeological sites in the Andes. The work highlights how remote sensing, field sampling and comparative study of Inca record-keeping can reshape interpretations of large-scale landscape features.
Published in Antiquity; initial aerial photos by Robert Shippee (1933). Original reporting appeared in Nautilus.