The Maya are an indigenous people of Mexico and Central America who have continuously inhabited the lands comprising modern-day Yucatan, Quintana Roo, Campeche, Tabasco, and Chiapas in Mexico, and southward through Guatemala, Belize, El Salvador and Honduras.
Around 250 A.D., the Maya entered what’s now known as the Classic Period, an era in which they built flourishing cities with temples and palaces, and population size peaked. However, by the end of the Classic Period, around 900 A.D., almost all of the major cities in what was then the heart of Maya civilization—the southern lowlands region, in present-day northern Guatemala and neighboring portions of Mexico, Belize and Honduras—had been abandoned. The collapse didn’t happen all at once; instead, it’s believed to have occurred over time from place to place, between about the late 8th and 925. Exactly why any of this transpired, though, is a mystery.
Clancy's comment: I'm always amazed at how sophisticated some of these cultures were.