> ## Content Index > Fetch the complete content index at: https://thehistoriesfiles.com/llms.txt > Use this file to discover other available public pages before exploring further. # Ecuador's Upano Valley: What a Lidar Survey Found Under the Amazon Forest - URL: https://thehistoriesfiles.com/upano-valley-ecuador-lidar-amazon-earthworks/ - Published: 2026-10-26T13:16:04.000Z - Updated: 2026-10-27T07:29:06.000Z - Description: A 2024 study in Science described thousands of earthen platforms, 15 settlements and long straight roads in Ecuador's Upano Valley. Here is what the researchers say it shows, and what is still unexplained. - Author: J E Cowie - Tags: News The study behind this story is not new. It appeared in the journal *Science* in January 2024, and it still reads as one of the more striking claims about the pre-Columbian Amazon. Archaeologists led by Stéphen Rostain of the French national research agency CNRS used aerial lidar data to describe a network of settlements, roads and farmland in the Upano Valley in eastern Ecuador. The paper is "Two thousand years of garden urbanism in the Upper Amazon" (Rostain, Dorison, de Saulieu et al., *Science*, vol. 383, issue 6679, pp. 183–189, DOI 10.1126/science.adi6317). ## What lidar did Lidar works rather like sonar, Rostain told CNRS News, except that it uses light rather than sound. The laser beam is fine enough to reach the ground through the forest canopy, and computer models then rebuild the terrain beneath it. Rostain told CNRS News that in 2015 Ecuador's National Institute of Cultural Heritage commissioned a private Russian company to carry out the aerial survey. His team was able to consult the results in 2021\. Excavations at several sites had already produced a lot of new material, he said, but the team still lacked an overall view of the valley. The scale of the survey area differs between accounts. Scientific American reported a 300-square-kilometre portion of the valley. Rostain described data collected over 600 square kilometres. ## Platforms, roads and drained fields Scientific American, reporting on the paper, described more than 6,000 earthen platforms that once supported houses and communal buildings in 15 urban centres, set among drained farmland and linked by roads. Rostain said the team had known of hundreds of platforms in the valley and found that there were thousands. The roads are among the most distinctive features. Rostain told CNRS News that the main roads "were perfectly straight, up to thirteen metres wide, and crossed the valley with no regard for its natural relief, cutting across both ravines and higher ground". Scientific American reported that these roads tended to be dug two or three metres deep into the landscape and were bordered by tall curbs of piled earth. Rostain told CNRS News that the builders' insistence on overcoming every obstacle, when going around them would often have been simpler, strongly suggests the roads had a symbolic function. He said they may have been used for processions and ritualised visits. That is his interpretation, not a finding the lidar can show directly. Analysis of the lidar data by Antoine Dorison, then a postdoctoral researcher at the ArchAm laboratory and a co-author of the paper, also pointed to a grid-like system of drains. Rostain told CNRS News that the system drained waterlogged soil so that crops could be grown in the gaps between platform complexes, and that agricultural terraces were built in the foothills of the surrounding mountain ranges. Excavation recovered remains and burnt seeds of manioc, sweet potato, fruits, beans and, above all, maize. He said the maize was ground to make chicha, a thick, sweet beer, and that traces of it were found in huge jars. Rostain and his colleagues call the combination of urban centres and fields "garden urbanism", according to Scientific American. José Iriarte, described by Scientific American in January 2024 as a University of Exeter archaeologist who studies pre-Columbian earth-builder cultures in Brazil and was not involved in the study, told the magazine that the infrastructure in Upano "is completely unprecedented in Amazonia and in Andean prehistory". ![the Sangay volcano in Ecuador, seen from a distance](https://thehistoriesfiles.com/content/images/2026/10/shot2_the-sangay-volcano-in-ecuador-seen-from-.jpg) the Sangay volcano in Ecuador, seen from a distance ## Why the valley, and why the volcano Rostain told CNRS News that the Upano Valley lies in the Amazonian section of the Andean foothills, between two mountain ranges, and is around a hundred kilometres long and twenty wide. It is dominated by the Sangay volcano, which he said has been in a constant state of eruption for decades. He said its ash makes the region especially fertile, and that local farmers told him they get three maize harvests a year. He said the valley was first occupied around 500 BC. He gave the end of that occupation as around 400–600 AD, while Scientific American reported that artifacts excavated from the house platforms suggest the settlements were abandoned sometime between 300 and 600 CE. ## An unexplained ending What happened to the people is not settled, and Rostain told CNRS News so himself. He said he has a theory, which "unfortunately has yet to be confirmed". Black layers above the uppermost layers containing evidence of dwellings suggest volcanic eruptions. He said the dates do not match any single event dramatic enough to make everyone flee. He suggested a series of smaller eruptions, or a climate crisis, might eventually have driven people away. His account also allows that the society may have collapsed and reverted to a tribal, forest-based way of life. His summary: "We have no firm explanation to offer at this time." On population, Rostain said the team was still trying to estimate it, but that the people must have rapidly depleted the valley's natural resources. ## Why it matters Rostain told CNRS News that when he began working in the Amazon nearly forty years ago, many archaeologists believed the region had been populated only by tribes similar to those found there today. He said he met scepticism in his early work in French Guiana. The Upano findings cut against that view. He said there are no sites like this elsewhere in the pre-Columbian Amazon, including Brazil, although similar urban systems are known from Mayan settlements in Guatemala and from [Teotihuacan in Mexico](https://thehistoriesfiles.com/caracol-te-kab-chaak-tomb-chase-teotihuacan/). The difference, he said, is that there are no stone buildings in the Upano. My reading is that the platform count and the road network are what carry the case. Lidar can show an earthwork's shape but not why people built it, and the road symbolism, the population and the collapse all remain interpretations or open questions. ## Sources Koppe, M. (2024) 'Ancient cities in the Amazon', CNRS News, available at: [https://news.cnrs.fr/articles/ancient-cities-in-the-amazon](https://news.cnrs.fr/articles/ancient-cities-in-the-amazon?ref=thehistoriesfiles.com) (Accessed: 26 October 2026). Rostain, S., Dorison, A., de Saulieu, G. et al. (2024) 'Two thousand years of garden urbanism in the Upper Amazon', Science, 383(6679), pp. 183–189, 11 January 2024, DOI: 10.1126/science.adi6317, available at: [https://doi.org/10.1126/science.adi6317](https://doi.org/10.1126/science.adi6317?ref=thehistoriesfiles.com) (Accessed: 26 October 2026). Smith, K.N. (2024) 'Ancient Amazon Civilization Developed Unique Form of "Garden Urbanism"', Scientific American, 11 January 2024, available at: [https://www.scientificamerican.com/article/ancient-amazon-civilization-developed-unique-form-of-garden-urbanism/](https://www.scientificamerican.com/article/ancient-amazon-civilization-developed-unique-form-of-garden-urbanism/?ref=thehistoriesfiles.com) (Accessed: 26 October 2026). ## Picture credits - Top picture. Image: Río Upano, ingreso a Macas — David C. S., [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/?ref=thehistoriesfiles.com) (via [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:R%C3%ADo%5FUpano,%5Fingreso%5Fa%5FMacas.jpg?ref=thehistoriesfiles.com)) - Sangay volcano, seen from Macas, Ecuador — photo by Dabit100, [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/?ref=thehistoriesfiles.com) (commons.wikimedia.org) ([source](https://commons.wikimedia.org/wiki/File:Volcan-Sangay-Ecuador.jpg?ref=thehistoriesfiles.com))