A research team then went on to discover a huge ancient city that they named “Valeriana” after a nearby freshwater lagoon.

The researchers say Valeriana, which may have been home to 30-50,000 people at its peak, probably collapsed between 800 A.D. and 1,000 A.D., for a complex set of reasons, including climate change.

“The growing consensus is that climate variability was a major factor causing stresses, adaptations and reactions, leading to more systemic unrest,” Canuto told NBC News on…