In around the 10th century AD, a whole vast empire that stretched from northern Central America to southern Mexico seemed to abruptly cease to exist and its people abandoned their large stone cities forever. They were the ancient city-states of the Mayan, whose people numbered in their millions.
No one knows exactly what happened to these people or why. There is evidence that a combination of drought, climate change, war, food shortages, and even disease contributed to their sudden downfall. But some theorists point to Mayan carvings that famously seemed to suggest a link with aliens and spaceships.
Whatever the cause, these highly sophisticated cities were swallowed up by the jungle and are only now being rediscovered with their magnificent pyramids and temples. An eerie reminder of a mysteriously vanished empire.