Beneath 1,350 square miles of dense jungle in northern Guatemala, scientists have discovered 417 cities that date back to circa 1000 B.C. and that are connected by nearly 110 miles of “superhighways” — a network of what researchers called “the first freeway system in the world.”

Scientist say this extensive road-and-city network, along with sophisticated ceremonial complexes, hydraulic systems and agricultural infrastructure, suggests that the ancient Maya civilization, which stretched through what is now Central America, was far more advanced than previously thought.

Mapping the area since 2015 using lidar technology — an advanced type of radar that reveals things hidden by dense vegetation and the tree canopy — researchers have found what they say is evidence of a well-organized economic, political and social system operating some two millennia ago.

The discovery is sparking a rethinking of the accepted idea that the people of the mid- to late-Preclassic Maya civilization (1000 B.C. to A.D. 250) would have been only hunter-gatherers, “roving bands of nomads, planting corn,” says Richard Hansen, the lead author of a study about the finding that was published in January and an affiliate research professor of archaeology at Idaho State University.

“We now know that the Preclassic period was one of extraordinary complexity and architectural sophistication, with some of the largest buildings in world history being constructed during this time,” says Hansen, president of the Foundation for Anthropological Research and Environmental Studies, a nonprofit scientific research institution that focuses on ancient Maya history.

These findings in the El Mirador jungle region are a “game changer” in thinking about the history of the Americas, Hansen said. The lidar findings have unveiled “a whole volume of human history that we’ve never known” because of the scarcity of artifacts from that period, which were probably buried by later construction by the Maya and then covered by jungle.