On July 29, 2026, a study published in the journal Nature reported finding more than 20,000 ancient structures hidden under the Amazon rainforest. The research team used a technology called lidar, which works like radar but with laser light instead of radio waves. Mounted on planes flying over the forest, lidar sends laser pulses down through the trees and measures how long they take to bounce back, building a detailed map of the ground that humans on foot could never see.

Most of the newly found structures are what researchers call geoglyphs: large designs made of earth, arranged in geometric shapes like circles and squares. They are concentrated near the border of Brazil and Bolivia, and possibly in neighboring countries, according to Live Science. Science confirmed that lidar was the main tool used and that most of the structures were geoglyphs.

The scale of the discovery is much larger than anyone expected. A 2023 study in Science by V. Peripato and colleagues had estimated that about 10,000 ancient structures might still be hidden across the Amazon. The new study appears to have passed that number. Before that, a 2017 study in PNAS by J. Watling and colleagues had documented over 450 geometric enclosures across about 13,000 km² of Acre state, Brazil. The jump from 450 structures in 2017 to over 20,000 in 2026 reflects a change in method: lidar can survey areas that are impossible to reach on foot or that have already been damaged by deforestation before archaeologists arrive.

The Max Planck Institute for Geoanthropology (MPI-GEA) pointed toward this kind of research in an October 2023 press release titled "Amazonian Rainforest Hides Thousands of Records of Ancient Indigenous Communities Under Its Forest Canopy." A December 2023 report by Mongabay noted that researchers had found 24 previously unreported ancient earthworks in the Amazon, and connected these findings to current struggles by Indigenous communities over land rights. Earlier in 2026, Daniel Pierce and Christopher Bodine used lidar data to find geoglyphs deep in the Amazon, as reported in February 2026, adding to a growing number of efforts using remote sensing in the region.

The broader context here is a long-running shift in how scholars understand the Amazon's past. For most of the twentieth century, the dominant view was that the Amazon's poor, worn-out soils could not support large, settled populations capable of building major structures. The growing list of geoglyph discoveries, from 450 enclosures in Acre to over 20,000 structures today, has steadily weakened that assumption. The sheer number of earthworks suggests that organized, possibly hierarchical societies lived in the southwest Amazon over long periods and reshaped the landscape on a large scale.

What the geoglyphs were used for remains debated. Possible explanations include ceremonial or ritual gathering places, defensive walls, water-management systems, and territorial boundary markers. The new Nature dataset is large enough that researchers may be able to test these competing ideas by studying how the sites relate to each other, how close they are to water sources, and how their shapes vary across different sub-regions.

There are also conservation stakes. Many of these earthworks are located in areas where deforestation is actively occurring, and some are likely destroyed before anyone can document them. The lidar record, in this sense, acts as a preservation tool: it captures an archaeological snapshot that the ground itself may not hold onto. As Mongabay reported, the overlap between ancient earthwork sites and contemporary Indigenous territories also places these findings within ongoing disputes over land and resource rights in the Amazon.

The study does not answer which specific precolonial peoples built the earthworks, over what time span, or how they organized the labor. What it does is set a baseline: over 20,000 structures, mapped at scale, that any future account of Amazonian history will need to explain.