Laser technology was used to survey digitally beneath the forest canopy, revealing houses, palaces, elevated highways, and defensive fortifications.
The landscape, near already-known Maya cities, is thought to have been home to millions more people than other research had previously suggested.
The researchers mapped over 810 square miles (2,100 sq km) in northern Peten.
Archaeologists believe the cutting-edge technology will change the way the world will see the Maya civilisation.
"I think this is one of the greatest advances in over 150 years of Maya archaeology," said Stephen Houston, Professor of Archaeology and Anthropology at Brown University.
Mr Houston told the BBC that after decades of work in the archaeological field, he found the magnitude of the recent survey "breathtaking". He added, "I know it sounds hyperbolic but when I saw the [Lidar] imagery, it did bring tears to my eyes."