Mayan civilization began in the pre-Classic period as well, but did not come into prominence until the Classic period (300–900CE). Development of this culture was agricultural villages during the pre-Classic period with city building during the Classic as social stratification became more complex. The Mayans built cities on the Yucatán Peninsula and west into Guatemala. In Chiapas, Mayan sites are concentrated along the state's borders with Tabasco and Guatemala, near Mayan sites in those entities. Most of this area belongs to the Lacandon Jungle.