A basin enclosed by mountains with cultural remains as early as 19,000 BC at Tlapacoya and 15,000 BC at Tlatilco. The Basin contains the current capital, Mexico City, Mexico, the remains of Aztec capital of Tenochtitlán, and the cities of Cuicuilco and Teotihuacán. Dry farming, swidden agriculture, chinampas, and irrigation have been used to cultivate the area. Important periods in the area's prehistory were from c 100 BC-650 AD and from 1200-1520 AD, before the Spanish conquest.