Lidar technology helped scientists detect a vast complex of ancient settlements in the Amazon rainforests (Credit: Stéphen Rostain and Lidar A. Dorison/ CC-BY-SA-2.0)

Researchers have always suspected that the Amazonian rainforests were once home to ancient cities. However, looking for remains of urban structures in the thick, remote forests was a difficult endeavor. But the use of Light Detection and Ranging, or Lidar, has been a game changer. The remote sensing technology uses laser light to help identify human-made features on the ground, such as walls, roads, or buildings. It has led to several exciting discoveries. The latest to be revealed is a network of 15 ancient settlements in the Upano Valley of eastern Ecuador in South America.

"It was really a lost valley of cities," said Stéphen Rostain, the study's lead author and director of Research at the National Center for Scientific Research in France (CNRS). "It's incredible."

A complex of earth platforms found in the Upano Valley (Credit: Stéphen Rostain/ CC-BY-SA-.2.0)

The discovery of what is believed to be the earliest and largest urban settlement in the Amazon, was revealed in the journal Science on January 11, 2024. It is the result of nearly 30 years of investigation by Rostain and his team. The 15 cities are sprawled out over 115 sq miles (300 sq km) on the foothills of the Andes Mountains. They are connected by a network of pathways and large, straight roads. The archeologists unearthed about 6,000 rectangular earthen platforms believed to be homes. The 66-foot by 33-foot (20-meter by 10-meter) dwellings were built around communal centers and plazas.

Large-scale archeological excavation on one earth platform in Upano Valley, Ecuador (Credit: Stéphen Rostain/ CC-BY-SA-2.0)

The scientists also found larger platforms that may have been used for civic or ceremonial functions. Between the settlements was evidence of cultivated land, complete with drainage fields and terraces. Many settlements were surrounded by ditches or other obstructions to keep intruders away. The carefully planned cities suggest the ancient people had surprisingly advanced engineering and building skills.

Rostain and his team assert that their discovery challenges the longstanding notion that the Indigenous people in the Amazon were primarily nomadic. They hope that further excavation in the area will reveal more about their beliefs and way of life.

Earth platform in Upano Valley, Ecuador (Credit: Stéphen Rostain/ CC-BY-SA-2.0)

"We have to think that all the Indigenous [people] in the rainforest were not semi-nomadic tribes lost in the forest, looking for food. They're a big variety, [a] diversity of cases, and some were also with [an] urbanistic system, with [a] stratified society," Rostain told CNN.