The remote Amazon river basin was once home to densely populated towns and villages, a scientific publication claims.
Science reports that this part of the Amazon, once thought to be virgin forest, has 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.
The ancient urban communities date back to before the first Europeans set foot in the Upper Xingu region of the Brazilian Amazon in the 15th Century.
Professor Mike Heckenberger, from the University of Florida, in Gainesville, says they are not cities but there is evidence of urbanism, built around towns.
"They have quite remarkable planning and self-organisation, more so than many classical examples of what people would call urbanism," he says.
The tell-tale traces included "dark earth" that indicated past human waste dumps or farming, and concentrations of pottery shards and earthworks.
The researchers also made use of satellite images and GPS navigation to uncover and map the settlements over the course of a decade.
The communities consisted of clusters of 60 ha towns and smaller villages spread out over the rainforest.
Like medieval European and ancient Greek towns, those forming the Amazonian urban landscape were surrounded by large walls. These were composed of earthworks, the remains of which have survived.
Each community had an identical road, always pointing north-east to south-west, which are connected to a central plaza.
The roads were always oriented this way in keeping with the mid-year summer solstice.
Evidence was found of dams and artificial ponds - thought to have been used for fish farming - as well as open areas and large compost heaps.
The people who once lived in the settlements are thought to have been wiped out by European colonists and the diseases they brought with them.
