Peru's ancient 'band of holes' was likely a thriving pre-Inca marketplace

A stretch of desert in Peru's Pisco Valley holds an unusual secret: more than 5,000 circular holes carved into the hillside, arranged in patterns so deliberate they were invisible until drones flew overhead.

For decades, archaeologists puzzled over Monte Sierpe—formally known as the "Band of Holes"—without a clear answer. Now researchers from the University of Sydney think they've cracked it. The site, they argue, was a bustling marketplace where traders, farmers, and fisherfolk gathered to exchange corn, cotton, and other regional goods. Later, the Inca adapted it into something more: a sophisticated accounting system.

How ancient commerce left its mark

The breakthrough came from combining old tools with new ones. High-resolution drone mapping revealed geometric patterns in the holes that had been invisible from ground level—the Pisco Valley's constant haze makes them nearly impossible to spot on foot. Soil analysis then provided the smoking gun. Researchers found traces of maize and reeds in the holes, materials used in food and weaving. Jacob Bongers, the digital archaeologist leading the study published in Antiquity, believes these holes once held baskets of goods stacked for trade.

The pattern itself tells a story. The holes mirror the structure of khipus—knotted-string recording devices the Inca used to track goods and tribute. This suggests a continuity: what began as a physical marketplace where people gathered and exchanged goods eventually transformed into a more abstract, administrative system under Inca rule. The site sits perfectly positioned between two Inca administrative centers and at the crossroads of major pre-Hispanic trade routes, making it an ideal hub for redistribution and barter.

Bongers describes the holes as "a type of social technology that brought people together." That framing matters. These weren't just random depressions—they were infrastructure. Someone designed them, maintained them, and organized them in a way that made sense to the community using them. The symmetry and segmentation visible in the drone footage suggest intentional planning, not accident.

This is the most detailed scientific study of Monte Sierpe since aerial photographs first brought it to attention in the 1930s. The new research doesn't just answer a 90-year-old question; it pushes back against decades of speculation by anchoring the site in evidence. Charles Stanish, co-author and professor at the University of South Florida, notes that the precision data "debunk decades of pseudo-archaeological speculation and reaffirm Indigenous innovation in landscape design and exchange."

What emerges is a picture of pre-Inca societies far more sophisticated than sometimes assumed—people who engineered their landscape to facilitate trade, who developed systems to track goods, and who built infrastructure that outlasted their own era. The Inca didn't invent these ideas; they inherited and refined them.