Peru’s 'Band of Holes': New Evidence for a Pre‑Inca Marketplace Later Repurposed for Inca Accounting

New research sheds light on a century‑old archaeological mystery

The Monte Sierpe “Band of Holes” in Peru’s Pisco Valley — about 5,200 aligned pits stretching nearly one mile (≈1.6 km) — has puzzled researchers since a 1933 aerial photograph first drew attention to the site. Recent work combining drone mapping and microbotanical analysis offers a fresh interpretation: the pits may have served as a pre‑Inca exchange hub and were later adapted by the Inca as part of a large‑scale accounting or tribute system.

What the team found

Researchers led by Jacob Bongers (University of Sydney) and Charles Stanish (University of South Florida) used low‑altitude drone imagery to produce precise maps of the site’s layout, revealing deliberate numerical and spatial patterning. Microbotanical analysis of sediment retrieved from some pits detected maize (corn) residues and remains of plants traditionally used for basketry, suggesting the presence or storage of commodities and containers.

“Why would ancient peoples make over 5,000 holes in the foothills of southern Peru? … we have produced some promising new data that yield important clues and support novel theories about the site’s use,” said Jacob Bongers, lead author of the study published in Antiquity.

Marketplace first, administrative system later

The authors propose a two‑phase interpretation. First, the pits may have functioned as temporary spots for traders to display or store goods at a periodic market — a regional meeting place for mobile merchants, llama caravans, coastal traders and local specialists. Second, after Inca expansion into the region, the same landscape appears to have been integrated into imperial systems of control and accounting.

Part of the argument rests on an apparent correspondence between the pits’ organization and the logic of quipu — the knotted‑string recording system used by the Inca. The site’s position between two known Inca administrative centers and at the intersection of pre‑Hispanic roads linking highlands and coast further supports the idea that Monte Sierpe could have been both a commercial hub and an administrative node.

Context and alternatives

Many earlier hypotheses remain plausible: defensive works, storage pits, agricultural beds, water or fog collectors, or ritual uses. The new evidence does not conclusively rule out these other functions, but the combination of patterned layouts, botanical traces, and logistical location strengthens the marketplace + later administrative adaptation interpretation.

Why it matters

This research illustrates how ancient communities modified landscapes to promote interaction and how social practices can be repurposed by later polities. If confirmed, Monte Sierpe expands our understanding of pre‑Inca exchange networks and highlights the diversity of Indigenous accounting and administrative strategies in the Andes.

Study: Bongers et al., Antiquity. Methods: drone survey and microbotanical sediment analysis. Site stats: ~5,200 pits; nearly 1 mile (≈1.6 km) long; pits ~3–6 ft (0.9–1.8 m) across and up to ~3 ft (≈0.9 m) deep.