The Maya civilization is a Mesoamerican civilization, noted for the only known fully developed written language of the pre-Columbian Americas, as well as its art, architecture, and mathematical and astronomical systems. Initially established during the Preclassic period, many of these reached their apogee of development during the Classic period (c. 250 CE to 900 CE), and continued throughout the Postclassic period until the arrival of the Spanish. At its peak, it was one of the most densely populated and culturally dynamic societies in the world.