A ridge above the Pisco Valley in southern Peru contains one of the most unusual large-scale constructions ever recorded. From ground level, the site appears as scattered depressions cut into a dry slope. From the air, the full structure becomes clear. A continuous band stretches for roughly 1.5 kilometers along the ridge, filled with thousands of evenly spaced holes arranged in sections, rows, and repeating blocks.
This site is known as Monte Sierpe, often referred to as the “Band of Holes.” It was first photographed from the air in the early twentieth century, and those images immediately raised questions that remained unanswered for decades. The structure shows no obvious buildings, no defensive walls, and no inscriptions explaining its use. Thousands of identical pits carved into a barren hillside created a visual that led to speculation across multiple fields and communities.
The scale alone sets it apart. Around 5,200 holes have been identified across the ridge. Each measures roughly one to two meters in diameter and up to a meter deep. These are not randomly distributed across the terrain. They are grouped into defined sections, and those sections are separated by clear gaps that form part of the layout.
The band itself varies between about 14 and 22 meters in width. It follows the ridge in a controlled line rather than spreading across the slope. The construction required coordinated effort over a large area, with consistency maintained across the entire length of the site.
Early explanations covered a wide range of possibilities. Storage, agriculture, water collection, and defensive use were all proposed. Some claims moved beyond conventional archaeology, driven by the visual impact of the site and the lack of a clear explanation. Without detailed mapping and analysis, the structure remained open to interpretation.
Recent work has focused on measurable features of the site rather than surface-level appearance. High-resolution drone mapping has revealed that the holes follow structured numerical patterns. These patterns repeat across different sections of the ridge. In some areas, rows contain eight holes repeated in sequence. In others, rows alternate between seven and eight. Certain sections contain totals that match those found elsewhere along the band.
These patterns are consistent across multiple sections. They do not reflect uneven digging or variation in terrain. The repetition shows that the layout was planned using fixed numerical arrangements rather than developed through random placement over time.
The structure also allows movement across and through the site. The gaps between sections act as crossing points along the ridge. Within each section, the spacing between holes allows people to move through the rows without obstruction. The layout is open rather than restrictive. It does not block access or channel movement into narrow paths.
Material found inside the holes provides further detail on how the site was used. Sediment samples contain traces of plant material, including maize and other species associated with human activity. These remains appear across multiple sections of the site rather than in isolated locations.
The hillside itself does not support crop growth. There is no water source on the ridge, and the conditions are too dry to sustain agriculture. The nearby river in the valley below provides water for farming, placing cultivation away from the site. The presence of plant remains in the holes indicates that material was brought there rather than grown in place.
Some of the identified plants do not disperse easily through wind. Their presence across the site requires direct transport. The distribution of these remains shows repeated use of the holes rather than a single phase of activity.
The position of Monte Sierpe places it within an active route network. Paths connecting coastal areas, inland valleys, and higher terrain pass through this region. The site lies between known centers associated with later administrative control. Movement of goods and people would have passed directly along this corridor.
The layout, material evidence, and location combine to form a structured system. The holes provide units. The sections provide grouping. The patterns provide consistency. The spacing allows movement and access across the entire site.
A comparable method of recording quantities exists in the same region. The Inca used khipus, systems of knotted cords that encoded numerical information through grouping and position. Numbers were expressed through structure rather than written symbols. Groups of cords represented categories, and knots represented quantities.
Monte Sierpe follows a similar principle using physical space. The holes act as units. The sections act as grouped sets. The numerical patterns create a consistent structure across the ridge. Instead of being carried as an object, the system is built into the landscape.
A layout of this type allows goods to be placed, counted, and compared directly. Filling a set of holes creates a visible quantity. Different sections can represent different groups or categories. Movement through the site allows interaction without obstruction.
During later control of the region, systems of tribute required goods to be collected and organized from multiple communities. A site positioned between administrative centers and along major routes provides a fixed location for that process. The repeated patterns across sections allow quantities to be measured in a consistent way across the entire structure.
The construction required coordination and planning from the outset. Thousands of holes cut into a ridge in repeating patterns cannot be explained by isolated activity. The layout does not show signs of irregular expansion. The patterns remain consistent along the full length of the site.
No evidence of defensive use has been identified. There are no associated weapons or fortifications. The structure does not match known agricultural systems used in similar environments. There are no burial patterns associated with the holes, and no evidence of mineral extraction within the site.
The holes contain material that was placed there. The layout follows repeatable numerical patterns. The structure allows movement, access, and visibility across the ridge. The location places it within a corridor of activity connecting multiple regions.
Monte Sierpe remains one of the largest structured ground-based systems identified in the region. Its appearance has driven speculation for decades, but detailed mapping and analysis show controlled design, repeated use, and a clear connection to movement and material handling across the landscape.
Source:
Bongers et al. (2025) – Indigenous accounting and exchange at Monte Sierpe
https://doi.org/10.15184/aqy.2025.10237
