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Hidden vestiges in Acre reveal a vast network of ancient paths, built by indigenous populations before the arrival of Europeans, with straight roads, connections to rivers, and access to monumental geoglyphs that still challenge researchers.
A network of 955 pre-Columbian roads and paths, with about 350 km of total length, was mapped in Acre by researchers from Brazil and Finland, revealing an ancient indigenous occupation more organized and connected than the current Amazonian landscape suggests.
Besides the territorial dimension, the survey identified 634 wide roads and 321 narrow ones in an area marked by geoglyphs, mounds, and other earth structures associated with indigenous societies prior to the arrival of Europeans on the American continent.
Published in April 2026 in the scientific journal Latin American Antiquity, the study combined satellite images and field checks to recognize ancient routes in the Acrean territory and assess their relationship with rivers, villages, and earth monuments.
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The analyzed area covers approximately 135 thousand km² in the southwest of the Amazon, where hundreds of large geometric drawings on the ground, such as squares, circles, and diamonds, have been identified more frequently in recent decades.
In many places, these marks appear surrounded by ditches or earthen walls, forming structures interpreted by archaeologists as possible spaces for gatherings, rituals, and collective activities, although part of their function still depends on further investigations.
The team responsible for the mapping includes Alceu Ranzi from the Federal University of Acre, Antonia Damasceno Barbosa from the National Institute of Historic and Artistic Heritage, Risto Kalliola from the University of Turku, and Martti Pärssinen from the University of Helsinki.
By bringing together Brazilian and Finnish researchers, the investigation crossed archaeological, geographical, and environmental data to understand how ancient populations occupied, modified, and connected different areas of Acre long before the formation of current Amazonian cities.
Pre-Columbian roads had straight layouts and spatial planning
Due to the regularity of the layouts, the ancient roads draw attention not only for their quantity but also for the way they were planned and distributed in a landscape marked by rivers, forests, and monumental earth structures.
A large part of the paths follows straight lines, and some roads seem to adhere to orientations linked to the cardinal points, suggesting spatial planning and possible use of astronomical references by the groups that built these routes.
Although many roads are less than 500 meters, some examples extend for several kilometers and reach 5.5 km in length, a dimension that indicates organized circulation between distinct areas of the Acre landscape.
Among the mapped structures, wide roads predominate, which in several cases exceed 15 meters in width from one edge to another, an uncommon measure for simple everyday trails in the forest.
This dimension reinforces the interpretation that part of the paths had a symbolic, ceremonial function or organized access to monumental areas, and not just a practical role of moving between nearby points.
According to the scientific article, the roads appear more frequently in areas denser with earth structures, especially near sets of geoglyphs, where the paths seem to organize circulation around the monuments.
The survey also indicated that more elaborate earth complexes tend to gather more paths than simple structures, while quadrilateral shapes have a stronger association with roads than rounded shapes.
Another important aspect is the relationship with rivers, as in cases where it was possible to identify the probable destination of the roads, about 40% of them led to riverbanks.
This pattern suggests a connection between villages, monuments, and circulation routes through the Amazon basin, while another 10% of the paths ended in geoglyphs or large excavated and compacted earth structures.
Acre Geoglyphs Connected to Rivers, Villages, and Ceremonial Areas
In an area northeast of Rio Branco, in the municipality of Boca do Acre, researchers highlighted the presence of 12 roads associated with the region where the Acre River meets the Purus River.
The location has archaeological importance because the rivers functioned as axes of movement, contact, and resource circulation, connecting different areas of the Amazon and expanding the reach of indigenous populations that lived in the region.
As they approach the geoglyphs, some roads fan out, creating wider and visually marked entrances for those arriving at the monumental spaces used in possible collective or ceremonial activities.
This design may have enhanced the visual perception of the courtyards for those approaching them, but the exact function remains under study, as archaeology works with material evidence and avoids turning hypotheses into certainty.
The low presence of domestic pottery in many geoglyphs supports the idea that these structures were not generally permanent residential areas, but places intended for other social uses.
Among the interpretations discussed by researchers, the spaces may have functioned as meeting grounds, festivity, or ritual practice areas, used by indigenous populations who managed the landscape in a planned and enduring manner.
The available datings associated with the geoglyphs indicate that this tradition began a few centuries before the Christian Era and extended until around the year 1000 AD, in different phases of territorial occupation.
After this period, from the 13th century onwards, the so-called mounds gained prominence, small artificial hills that functioned as village centers and points for radiating paths in new forms of territorial organization.
Lidar can reveal new structures hidden by the forest
Almost half of the identified roads still do not have an evident destination in the analyzed images, which leaves open the function of many paths and indicates that the ancient network may have been more complex than is known today.
These paths may have led to cultivation areas, collection points, or places currently covered by the forest, but this function has not been confirmed with certainty and remains treated as a hypothesis dependent on new evidence.
For this reason, the study presents these paths as part of a still incomplete network, whose interpretation requires cross-referencing images, excavations, datings, and new technologies capable of revealing marks hidden under the vegetation.
Alceu Ranzi told Folha that “the more technology and observations advance, the more we perceive the presence of roads and paths and the connection between them and the monuments.”
The statement summarizes the role of remote sensing tools in revising the idea of an ancient Amazon little modified by human societies, especially in regions where the forest has returned to cover ancient structures.
Among the most promising resources is Lidar, a technology based on laser pulses capable of penetrating the vegetation cover and revealing changes in the terrain under the forest without relying on vegetation removal.
As part of the known structures only appeared after deforestation, the method can identify paths and geoglyphs still hidden by the canopy, expanding the archaeological map of Acre without requiring new clearings in the forest.
The research reinforces that the current territory of Acre preserves marks of indigenous societies capable of planning paths, erecting monumental structures, and connecting different areas by land and rivers over several centuries.
More than isolated vestiges, the pre-Columbian roads of Acre indicate a landscape built in layers, in which circulation, ceremony, and territorial organization were part of the same social and environmental system.
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