The Amazon rainforest has inspired countless tales of lost civilizations, and the more archaeologists explore the lush region, the more it lives up to this legendary reputation.
Now, a team of archaeologists and satellite imagery specialists have discovered the remains of a previously unknown civilization that flourished around 1250 to 1500 AD, just before the European colonization of the Americas. The find, which includes captivating images of geometric earthworks, is described in a paper published Tuesday in Nature Communications, led by University of Exeter archaeologist Jonas Gregorio de Souza.
“The results show that an 1,800 kilometer stretch of southern Amazonia was occupied by earth-building cultures living in fortified villages,” de Souza’s team concluded in the paper, a discovery that calls “for a re-evaluation of the role of this region for Pre-Columbian cultural developments and environmental impact.”
These peoples lived away from major rivers in the Brazilian state of Mato Grosso. There may have been as many as one million individuals living in over 1,000 small villages in this area, which is far more than previously estimated. The “interfluvial” habitat they occupied—the lands between floodplains—have been “archaeologically neglected,” the researchers said, because of a prevailing assumption that Pre-Columbian societies would have kept close to prominent waterways.
But these communities not only settled in these relatively unexplored regions, they shaped their landscapes into geometric patterns, called “geoglyphs,” that remain etched there to this day. Satellite images of newly explored sites within the Upper Tapajós Basin revealed 104 examples of earthworks, in the form of circles, hexagons, and squares. They range in diameter from 30 to nearly 400 meters across, and some overlap with each other, or contain smaller shapes within larger enclosed ditches.
The function of the geoglyphs is not definitively known, but many appear to have been unoccupied, perhaps serving a ceremonial purpose. Expeditions to some of the sites revealed by the satellite images found that villages were sometimes located within or around these earthworks.
Based on these findings, de Souza’s team calls into question “the prevalent idea that major waterways were the main communication routes in Amazonia,” showing that much of the underexplored interfluvial regions contained a sprawling network of villages ranging in size from 20 to 2,500 individuals. It goes to show that the archaeological mysteries of deep Amazonia have barely been scratched, and there is much to learn about the human history of this vitally important biome.
This article originally appeared on Motherboard.