Such special structures as the Caracol at Old Chichen and the observatory at Copan had an astronomical purpose. They were operated by the priests to devise and maintain a calendar more accurate than any except the Gregorian. The Maya invented a numerical system that involved the concept of zero, which was positional like the decimal system but based on 20 instead of 10. The symbols were dot-and-bar combinations and hieroglyphs. Scholars developed a system of hieroglyphic writing similar to the ideographic type of the ancient Egyptians but more primitive. The glyph inscriptions with narrative content are being translated with partial success.
Many buildings of Yucatan in the Puuc style are decorated with the face of Chac, the Mayan rain god, an all-important deity in a society dependent on agriculture. Chac can be recognized by an elephant tusk nose. Sometimes there are three or four Chacs stacked over a doorway, giving security in numbers, and on the corners of buildings with eyes surveying two sides at the same time. The use of Chacmools--the bearers of messages to the pantheon of deities--so prominent at Chichen Itza, was introduced by the Toltecs of Tula from Central Mexico.
The Maya located in the highlands lived in a third type of physical environment--the volcanic mountains and intermontane valleys of Guatemala. Kaminaljuyu arose as a notable urban center in the classic period, much influenced by Teotihuacan in Central Mexico. The region was harshly conquered by Pedro de Alvarado in 1524 after the submission of Tenochtitlan, the Aztec capital. The myths and traditions of the past are preserved in the Popul Vuh, the sacred