An ancient Amazonian civilization built enormous circles, squares, and other structures of geometry in Brazil’s rainforest around the time the Greek mathematician Pythagoras lived. Archaeologists have now identified hundreds of previously unknown earthworks, revealing the scale of these ancient building practices.
The study, published in the journal Nature, documented 396 previously unknown structures using laser-based mapping technology. Researchers estimate that the region could contain between 24,000 and 30,000 earthworks.
Ancient Amazonian builders created complex geometric designs
The structures belonged to the Aquiry civilization, which occupied parts of what are now the Brazilian states of Acre and Amazonas. Researchers identified geoglyphs, large geometric designs formed by digging trenches into the ground. These included circles, squares, pentagrams, and octagons. Some featured more elaborate arrangements, including circles enclosed within squares.
Earlier archaeological investigations dated some of the earthworks to about 2,500 years ago, around the period when the ancient Greek mathematician Pythagoras lived in the sixth century B.C. Geographer Alceu Ranzi of the University of Acre compared the geometric skills of the Amazonian builders with those of ancient Greek mathematicians. “At the same time that Pythagoras was in ancient Greece doing his theorem, we had people here in Amazônia doing geometry,” Ranzi said.
While Pythagoras studied geometry in ancient Greece, another civilization was creating massive circles, squares and intricate designs deep in the Amazon.
Researchers have now uncovered hundreds of ancient earthworks hidden beneath the rainforest.#Archaeology #AncientHistory pic.twitter.com/96BRrZiQKV
— Tom Marvolo Riddle (@tom_riddle2025) November 13, 2026
Archaeologists found limited evidence of everyday human activity at several sites. This suggests that some structures may have served ceremonial purposes rather than functioning as settlements.
Researchers uncover evidence of a large ancient population
The research team, led by Martti Pärssinen of the University of Helsinki, surveyed 4,497 square kilometers (1,736 square miles). They documented 432 earthworks, including 396 previously unknown structures. Researchers estimate that between 1.25 million and 3 million people may have lived in the Aquiry region at its peak between A.D. 100 and 300.
Many structures stood far from major rivers, where archaeologists previously expected fewer settlements. The findings add to earlier discoveries of ancient Amazonian cities.
Laser technology reveals structures beneath the forest
Researchers used lidar technology to identify earthworks hidden beneath dense vegetation. The system sends laser pulses toward the ground to create detailed 3D maps, allowing archaeologists to detect structures without clearing the forest. Similar technology has helped researchers identify ancient structures in Ecuador’s rainforest.
The discoveries also raise concerns about protecting Indigenous heritage. Some communities worry that publicly available maps could expose sacred locations. Pärssinen said researchers removed images showing earthworks within officially recognized Indigenous territories before releasing their findings.
The study also suggests that ancient communities influenced the rainforest’s environment. Brazil nut trees found near the earthworks may reflect past cultivation and forest management. Researchers say the discoveries challenge the idea that large parts of the Amazon remained untouched by human activity before European arrival.
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