New Study Suggests Peru’s Mysterious 5,200 Holes Were Created for Ancient Trade and Inca Accounting

A long-mysterious series of more than 5,200 aligned holes carved across nearly a mile of the Pisco Valley in southern Peru may finally have a clearer origin story. New research suggests the vast formation, known as Monte Sierpe, likely served as a large barter-based marketplace for a pre-Inca civilization, and was later adapted by the Inca Empire as a massive accounting system.

The formation, informally known as the “band of holes,” has puzzled archaeologists since aerial photos were first published in 1933. Without written records, theories over the years have ranged from agriculture and water collection to defensive structures and even extraterrestrial involvement. But a new study published in the journal Antiquity offers evidence that points toward economic use.

Researchers used drone mapping and microbotanical analysis to better understand the massive site. Each of the thousands of holes measures roughly 3 to 6 feet across and up to 3 feet deep. Drone imagery revealed organized sections separated by empty spaces, while pollen trapped inside the holes showed traces of maize and plants commonly used for weaving baskets. The findings suggest goods may have been placed in the holes for exchange, likely by people of the pre-Inca Chincha Kingdom between AD 1000 and 1400.

As the Inca Empire expanded, the research team believes the holes took on a second purpose: accounting. The segmented layout resembles the structure of Inca khipus, knotted strings used to record numbers and manage goods. A khipu found in the same region contains more than 80 groups of cords, hinting at similar record-keeping patterns. Monte Sierpe sits between major Inca sites and ancient road networks, supporting the idea that it may have tracked tribute or taxation.

While more radiocarbon dating is underway and the connection to khipus is still being studied, researchers say the new evidence rules out many earlier theories. The site also appears to have remained in use into the colonial era, until the Spanish failed to incorporate it into their economic systems.

Experts say the findings highlight how much remains unknown about ancient Andean economies and how Indigenous societies organized trade long before European contact. Archaeologists emphasize the importance of interpreting such heritage through both scientific evidence and Indigenous perspectives to ensure accurate understanding of Peru’s past.

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