National Geographic really does specialize in that whole lost jungle city thing, doesn’t it? And it’s so nice when they actually deliver faint traces of long-gone civilizations:
Satellite images of the upper Amazon Basin taken since 1999 have revealed more than 200 geometric earthworks spanning a distance greater than 155 miles (250 kilometers).
Now researchers estimate that nearly ten times as many such structures—of unknown purpose—may exist undetected under the Amazon’s forest cover.
At least one of the sites has been dated to around A.D. 1283, although others may date as far back as A.D. 200 to 300, said study co-author Denise Schaan, an anthropologist at the Federal University of Pará in Belém, Brazil.
The discovery adds to evidence that the hinterlands of the Amazon once teemed with complex societies, which were largely wiped out by diseases brought to South America by European colonists in the 15th and 16th centuries, Schaan said.
There’s a photograph of one of the sets of earthworks at the link. They don’t know who built them – no one was supposed to be living in the Amazon uplands at all – but they do know that the same people were in the river’s floodplain as the uplands, and building the same sorts of… things.