Excerpts from Books and Wikipedia
"A group of tribal peoples, loosely related by language and culture, building cities that tended to act in alliance, became distinct enough for us to give them a name: the Maya. Southwest of the Mayan territory, in the fertile plain known as the Valley of Oaxaca, another collection of small tribal territories was united (mostly by force) under the leadership of the strongest city among them, Monte Alban: this allows us to see them also as a single people, the Zapotec. . . . The third powerful kingdom on the land bridge worked out the passage of time in a slightly different way. This kingdom was centered around the city of Teotihuacan, which in AD 500 was the sixth largest city in the entire world. . . . “Teotihuacan” is the name given to the city, long after its fall, by the Aztecs (who do not enter the historical record for some centuries yet). . . . What happened to the Mayan cities is even less clear. . . . But most of the Mayan records—the elaborate calendars, genealogies, and chronologies—break off at 534, and the silence lasts for nearly a century." [Bauer: Medieval World, p. 186-92] "Between 985 and 1050, the biggest Mayan cities collapse." [Bauer: Medieval World, p. 574]