Amazon LiDAR: Hidden Ancient Cities

For centuries, the Amazon rainforest was viewed as a pristine wilderness sparsely populated by small, nomadic tribes. That view has been shattered. Recent groundbreaking research published in the journal Science has utilized advanced laser technology to peel back the dense jungle canopy. What researchers found underneath changes our understanding of human history in the Americas: a massive, complex network of ancient cities hidden in the Upano Valley of eastern Ecuador.

The Discovery in the Upano Valley

In January 2024, archaeologist Stéphen Rostain and his team from France’s National Center for Scientific Research (CNRS) revealed the results of two decades of fieldwork combined with cutting-edge remote sensing. While Rostain had been excavating in the Ecuadorian Amazon since the 1990s, the dense vegetation made it nearly impossible to see the “big picture” of the settlements.

Using LiDAR (Light Detection and Ranging) technology, the team surveyed approximately 300 square kilometers (about 116 square miles) of the Andean foothills. The scans exposed more than 6,000 earthen platforms arranged in geometric patterns. These were not isolated huts. They were part of an integrated system of urban settlements connected by a vast network of straight roads and canals.

The scale of this discovery implies a population density far higher than previously thought possible for the ancient Amazon. Some estimates suggest that at its peak, this specific region could have been home to 10,000 to 30,000 people, a population comparable to London during the Roman era.

How LiDAR Strips Away the Jungle

The technology responsible for this revelation is LiDAR. It works by mounting a laser scanner on an aircraft (in this case, a plane carrying sensors) that flies over the target area. The sensor fires hundreds of thousands of laser pulses per second toward the ground.

Here is how it reveals hidden structures:

• Penetration: While many pulses hit leaves and trees, a small percentage reach the forest floor.
• Reflection: The light bounces back to the sensor, measuring the distance with extreme precision.
• Digital Deforestation: Computer algorithms process the data to remove the “noise” created by the vegetation.

The result is a 3D topographic map of the ground surface. This digital model highlights unnatural shapes, such as square foundations, long straight lines, and dug-out canals, which are invisible to the naked eye from the air or the ground.

Architecture of the Earth: Roads and Mounds

The civilization found in the Upano Valley did not build with stone like the Maya or the Inca. Instead, they were masters of earthworks. The LiDAR data revealed five major settlements and ten smaller ones, all densely packed with structures.

The Platforms

The most common features are rectangular earthen platforms. These measure about 20 meters by 10 meters (66 by 33 feet) and stand 2 to 3 meters high. Scientists believe these were the foundations for wooden houses. These platforms are typically arranged around a central square plaza, indicating a community-focused lifestyle.

The Road Network

Perhaps the most stunning finding is the sophisticated road infrastructure. The LiDAR maps show a complex web of roads connecting the different settlements.

• Straightness: The roads run in remarkably straight lines, suggesting advanced planning and engineering.
• Size: Some of the main roads are up to 10 meters (33 feet) wide and extend for 10 to 25 kilometers (6 to 15 miles).
• Construction: To keep the roads usable during the Amazon’s intense rainy seasons, the builders dug down to create a stable surface and piled the earth on the sides.

A "Garden City" Civilization

This discovery challenges the long-held belief that the Amazon soil was too poor to support large-scale agriculture or dense urbanization. The civilization in the Upano Valley, occupied roughly between 500 BCE and 300 to 600 CE, practiced a form of urbanism that looks different from European or Middle Eastern cities.

Researchers describe this as a “garden city” or “green urbanism.” The empty spaces between the residential platforms were not wasted; they were agricultural fields. The inhabitants likely farmed maize, manioc (cassava), and sweet potatoes right next to their homes.

The LiDAR scans also revealed extensive drainage canals and terraces. These hydro-engineering feats managed the water flow, preventing floods in the living areas while irrigating the crops. This level of environmental modification proves that these ancient people were not passive inhabitants of the forest but active shapers of their landscape.

Rethinking Amazonian History

The findings in Ecuador are part of a larger trend in archaeology. Similar discoveries have been made in the Bolivian Amazon (the Llanos de Mojos) and parts of Brazil. However, the Upano Valley sites are significantly older than many other known Amazonian complex societies.

The culture responsible for these structures is generally identified as the Kilamope and later the Upano cultures. Their ability to organize labor to build thousands of mounds and miles of wide roads points to a stratified society with leaders, engineers, and a dedicated workforce.

This evidence forces history books to be rewritten. The Amazon was not a demographic void before the arrival of Europeans. It was a bustling hub of human innovation, home to millions of people who built civilizations entirely out of biodegradable materials like wood and earth. LiDAR is simply finally allowing us to see what nature reclaimed over the last millennium.

Frequently Asked Questions

What is LiDAR and how is it used in archaeology? LiDAR stands for Light Detection and Ranging. It uses laser pulses fired from an aircraft to measure distances to the ground. By filtering out the data points that hit trees and leaves, archaeologists can create a 3D map of the ground surface, revealing man-made structures hidden under dense vegetation.

Where exactly were these cities found? The cities were discovered in the Upano Valley, located in the eastern foothills of the Andes mountains in Ecuador. The survey covered roughly 300 square kilometers.

How old are these Amazonian cities? The settlements were occupied roughly between 500 BCE and 300 to 600 CE. This makes them more than 1,000 years older than other famous Amazonian complex societies previously discovered.

Why were these cities not found earlier? The structures were built from earth and wood, not stone. Over centuries, the dense Amazon rainforest grew over the mounds and roads, hiding them from sight. Traditional ground surveys are difficult and slow in the jungle, making the scale of the settlements impossible to grasp without aerial laser scanning.

Did the people who lived there destroy the forest? Evidence suggests they practiced “agroforestry” or garden urbanism. They modified the land to farm and build, but they integrated their food production within their cities. They did not clear-cut the forest in the modern industrial sense but rather managed the forest to support a large population.