The BBC reports:
The remote Amazon river basin was once home to densely populated towns and villages, Science journal reports.
This part of the Amazon, once thought to be virgin forest, has in fact been touched by extensive human activity.
Researchers found traces of a grid-like pattern of settlements connected by road networks and arranged around large central plazas.
There is also evidence of farming and wetland management, including possible remains of fish farms.
The settlements are now almost completely overgrown by rainforest.