Researchers have found the ruins of a long-lost Mayan megalopolis under Guatemalan forests in a “major breakthrough”, National Geographic reported on Thursday. The landscape they have found was probably home to millions of people centuries ago.

The research used laser technology to find over 60,000 houses, palaces, canals and highways buried over 2,100 sq km in northern Petén. The findings were made by an international collaboration of researchers, headed by the PACUNAM Foundation, a Maya cultural and natural heritage organisation.

The Mayan civilisation was at its peak about 1,500 years ago.

The technology, LiDAR, or “Light Detection and Ranging”, helps digitally discover archaeological wonders invisible to the naked eye through remote sensing. Some archaeologists have called it “magic”, according to the BBC.

“I think this is one of the greatest advances in over 150 years of Maya archaeology,” Stephen Houston, professor of archaeology and anthropology at Brown University, told BBC.

“The LiDAR images make it clear that this entire region was a settlement system whose scale and population density had been grossly underestimated,” said archaeologist Thomas Garrison. Everything is now turned on its head, he told BBC.

“Most people had been comfortable with population estimates of around 5 million,” archaeologist Estrada-Belli told National Geographic. “With this new data it’s no longer unreasonable to think that there were 10 to 15 million people there.”

The survey was the first phase of a three-year project that will map more than 14,000 sq km of Guatemala’s lowlands.