Giant desert figures in Peru only make sense from the sky

Across a high, dry plateau in southern Peru, generations of people scraped away the desert’s dark surface stones to expose the pale soil underneath, tracing lines and shapes across a stretch of land roughly 80 kilometers long. From ground level, most of it reads as scattered trenches. It was not until aircraft began crossing the region in the twentieth century that the full scale of what had been drawn there became clear.

Etched, not built, into the desert floor

The geoglyphs were made between roughly 500 BC and 500 AD, spanning what researchers divide into a Paracas phase from 400 to 200 BC and a later Nazca phase running to about 500 AD. Builders removed the reddish-brown, iron oxide-coated pebbles that blanket the desert surface, exposing a yellow-grey subsoil underneath and creating trenches typically 10 to 15 centimeters deep. Most lines run slightly wider than 33 centimeters, though some narrow to 30 centimeters and others widen to nearly 1.8 meters. Altogether, the combined lines stretch more than 1,300 kilometers across an area of roughly 450 square kilometers, preserved for two millennia by one of the driest, most windless climates on Earth, where morning mist hardens the exposed, lime-rich subsoil into a crust that resists erosion.

Hummingbirds, monkeys and a 134-meter condor

While hundreds of the geoglyphs are simple straight lines or geometric shapes, more than 70 take the form of animals and plants, including a hummingbird, spider, heron, dog, lizard, a monkey and a human figure, according to the catalog of documented designs. Some have been precisely measured: the hummingbird spans 93 meters, the condor 134 meters, the monkey 93 by 58 meters, and the spider 47 meters, with the largest figures anywhere on the plateau stretching close to 370 meters. Because the designs were drawn as continuous lines across such enormous distances, they read clearly only from an elevated vantage point, something the people who made them could only have achieved from nearby foothills or, according to some researchers, with the aid of simple sighting and surveying methods rather than flight. Archaeological surveys have turned up wooden stakes driven into the ground at the ends of some lines, and radiocarbon dating one of those stakes helped establish the age range now used for the wider design complex.

An observatory theory that never fully held up

American historian Paul Kosok is generally credited as the first scholar to study the lines closely, flying over the plateau in 1940 and 1941 while researching ancient irrigation systems and noticing that one shape formed a bird. Kosok, working with German mathematician and archaeologist Maria Reiche, proposed the lines functioned as a kind of astronomical calendar, marking where the sun and other celestial bodies rose on significant dates such as the solstice. Reiche spent decades studying and helping protect the site around this theory, and a later protégé argued specific figures represented constellations. Archaeoastronomy specialists Gerald Hawkins and Anthony Aveni tested the idea rigorously and concluded, in 1990, that the evidence was not strong enough to support a systematic astronomical explanation, leaving the purpose of most individual figures unresolved. Other researchers have since proposed the lines traced paths to water sources or aquifers, or served as routes for religious pilgrimage tied to fertility and rainfall.

Proving the figures needed no ancient astronauts

The lines’ scale and isolation made them an early target for pseudoscientific claims, most famously Swiss writer Erich von Däniken’s 1968 book “Chariots of the Gods?,” which argued the geoglyphs served as landing strips for extraterrestrial visitors. Maria Reiche and other archaeologists rejected the idea at the time, and researchers later demonstrated the figures could be built using only tools and surveying methods available to the Nazca people. Investigator Joe Nickell reproduced several of the largest figures in the early 2000s using period-appropriate technology, work Scientific American described as remarkable in its exactness, and a small team recreated even the biggest designs within days using wooden stakes and cord, with no aerial assistance required at any stage.

Machine learning is still turning up new figures

Discovery has not stopped with the classical roster of shapes. A Japanese team from Yamagata University has surveyed the plateau since 2006, documenting around 100 new geoglyphs by 2012. In 2019, the university’s researchers working with IBM Japan announced 143 additional figures, one located with the help of machine learning. A 2024 collaboration between Yamagata University’s Nazca Institute and IBM Research pushed that further, using artificial intelligence to screen more than 1,300 candidate sites over roughly 1,440 field-survey labor hours, confirming 303 previously unknown geoglyphs depicting parrots, cats, monkeys, killer whales and human figures, work conducted under permission from Peru’s Ministry of Culture. The site was designated a UNESCO World Heritage Site in 1994, though conservationists continue to flag threats from squatters, heavy rain and, on at least one occasion, vehicles straying off nearby roads onto ground that has stayed essentially undisturbed for roughly two thousand years. Researchers expect the tally of known geoglyphs, which stood at 358 as recently as 2022, to keep climbing as AI-assisted survey work continues across the plateau.

This article was produced with the assistance of AI and reviewed by an editor.

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