Valeriana has the “hallmarks of a capital city” and was second only in density of buildings to the spectacular Calakmul site, around 100km away (62 miles).
It is “hidden in plain sight”, the archaeologists say, as it is just 15 minutes hike from a major road near Xhipul where mostly Mayan people now live.
There are no known pictures of the lost city because “no-one has ever been there”, the researchers say, although local people may have suspected there were ruins under the mounds of earth.
The city, which was about 16.6 sq km, had two major centres with large buildings around 2km (1.2 miles) apart, linked by dense houses and causeways.
It has two plazas with temple pyramids, where Mayans would have worshipped, hidden treasures like jade masks and buried their dead.
It also had a court where people would have played an ancient ball game.
There was also evidence of a reservoir, indicating that people used the landscape to support a large population.
In total, Mr Auld-Thomas and Prof Canuto surveyed three different sites in the jungle. They found 6,764 buildings of various sizes.
