Valley of Holes: 5,200 Pits on Monte Sierpe — From Pre‑Inca Market to Inca Tax Depot

Perched on Monte Sierpe in Peru's Pisco Valley, a sinuous 1.5 km sweep of roughly 5,200 man‑made pits has puzzled observers for generations. Carved before the 1532 Spanish conquest, the so‑called "Valley of Holes" is now argued to have been a bustling pre‑Inca marketplace that the Inca later repurposed as a fiscal center.

Location and cultural context

The site sits about 200 km south of present‑day Lima at a strategic crossroads where coastal fisheries, agricultural plains and Andean highland routes meet. At the start of the first millennium the hilltop lay on the edge of the Chincha polity, a maritime and agricultural society known for intensive farming (including the use of guano) and coastal sailing. The Chincha likely began construction of the pits; their territory was incorporated into the Inca Empire around 1480, though local elites retained influence.

What the site looks like

The pits form a continuous, snake‑like line across the ridge. They are organized into repeatable clusters: roughly a dozen rows per cluster with about six pits per row, and clear circulation space between rows and clusters. The regular arrangement, scale and spacing make the site well suited to activities that required many simultaneous participants and orderly display areas.

New evidence: soil, seeds and trade goods

In a recent study published in Antiquity, researchers mapped the complex with high‑resolution aerial photography and took soil samples from 19 pits. The samples yielded plant remains absent from surrounding soils, including maize, cotton and members of the brassica family, as well as Humboldt's willow — a coastal riparian species used for basket weaving. While mountain plants might travel by wind, cultivated crops and coastal flora strongly imply human carriage and exchange.

Marketplace hypothesis and Inca use

Archaeologists propose that each clustered group of pits functioned like stalls or categories in a market, with goods displayed in individual pits and pathways allowing shoppers and carriers to circulate. Later, under Inca administration, Monte Sierpe's position on major trade routes and its existing infrastructure would have made it a logical site for collecting quotas and redistributing resources as part of the empire's rigorous tributary system.

Quipu, record‑keeping and future avenues

The Inca tracked labor and resources using quipus — knotted‑string records that encoded numeric and possibly non‑numeric information. A quipu recovered near the Pisco Valley appears to document large‑scale accounting data and may relate to activities at Monte Sierpe, though its precise meanings remain debated. Advances in computational analysis, including machine learning and new statistical techniques, are improving researchers' ability to decipher quipus and could clarify connections between the record and the site.

Why it matters

The Valley of Holes offers a rare glimpse into pre‑Inca economic life and the way the Inca integrated existing regional systems into their administrative network. Whether read as a marketplace, a tax depot, or both in successive phases, Monte Sierpe helps historians understand exchange, mobility and state organization on the Peruvian coast and foothills.