For centuries, the Amazon rainforest has been the subject of stories about hidden cities and lost riches. The most famous of these is El Dorado, a legend born in the 16th century from accounts of the Muisca people of Colombia, whose chief would coat himself in gold dust and make offerings to a sacred lake. As the story spread across Europe, a ritual became a rumor, and a rumor became a city of gold. It was never found, because it never quite existed, but that has done little to stop people from looking.

Not all of the Amazon's lost cities are legends, though. In Bolivia's Llanos de Mojos region, scientists using airborne lidar (a technology that fires infrared beams from aircraft to map terrain hidden beneath the forest canopy) have identified the remains of a large urban civilization built by the Casarabe people between roughly 500 and 1400 C.E. The sites include pyramids that once stood over 70 feet tall, raised roads connecting outlying settlements, and large reservoirs suggesting the society struggled with drought at some point. Eleven of the sites found in 2022 were completely unknown before the survey. What happened to the Casarabe is still unclear, but their cities seem to have been abandoned well before Spanish contact.
 

Similar discoveries have been made in Ecuador's Upano Valley, where archaeologists identified 15 settlements across 120 square miles, with flood barriers, drainage canals, and neighborhoods divided by social class. In Brazil, near the headwaters of the Xingu River, surveys located over 20 interconnected settlements spread across thousands of square miles, close to where British explorer Percy Fawcett disappeared in 1925 while searching for a lost civilization he called simply "Z."