Used by the Maya for travel and transporting goods, the causeways were identified in the Mirador Basin, which lies in the far northern Petén region of Guatemala, within the largest tract of virgin tropical forest remaining in Central America. Also known as the Kan Kingdom, El Mirador is considered the cradle of Mayan civilization. Prior to its abandonment in 150 A.D., it was the largest city-state in the world both in size — 833 square miles — and population. It boasted the largest known pyramid in Central America, and was home to at least one million people. Researchers have known...