The principal river of the state is the Rio de las Balsas or Mescala, which, having its source in Tlaxcala, flows entirely across the state from W.
Tributaries of the Mescala drain the western quarter of the state, among which is the Atoyac or headstream of the Mescala, which rises in Tlaxcala, and flows across the state of Puebla.
A strange stone sculpture of the so-called Chac-Mol type, known before only from the country of the Tarascs, from Tlaxcala and Chichen Itza, was discovered in Salvador (Ahuachapan).
The largest rivers of Mexico are: the Rio Grande de Santiago, called the Lerma above Lake Chapala, rising in the state of Mexico and flowing westward across Guanajuato, Jalisco and Tepic to the Pacific coast, with a total length of 540 m., celebrated for its deep canyons and waterfalls; the Rio de las Balsas, or Mescala, which rises in Tlaxcala and flows south and west to the Pacific with a course of 426 m.; the Yaqui, which rises in western Chihuahua and, after breaking through the northern ranges of the Sierra Madre Occidental, flows south-westerly across Sonora to the Gulf of California, with a length of 390 m.; the Grijalva, also called the Chiapas on its upper course, which has its sources in the state of Chiapas and flows north-west and north across Tabasco to the Gulf of Mexico, with a total length of 350 m.; the Fuerte, which rises in southern Chihuahua and, after breaking through the sierras, flows south-west across Sinaloa to the Gulf of California, with a course of 340 m.; the Usumacinta, which is formed by the confluence of the Chixoy and Pasion on the east frontier of Chiapas, and flows north-west across Tabasco to the Grijalva, with a course of 330 m.; and the Panuco, which has its source in the north-west of the state of Mexico and flows north-eastward to the Gulf of Mexico.
North of the national capital, and it is not improbable that the people of Cholula, Texcoco and Tlaxcala at the time of the Spanish invasion were occupying the sites of older Toltec towns.