The Classic Mayan civilization extended from the Mexican Yucatan Peninsula into Central America, from about 250 AD (CE) to 900 AD (CE). Chichen Itza in Mexico has some of the most impressive pyramids, temples, palaces and other structures of the Mayan competing city-states. They were intellectual peoples, with mathematical, astronomical and engineering skills, but religion was the primary source of these sophisticated activities. El Caracol observatory seems to have been built because the Mayans thought the movements of the sun, planets and stars were related to the activities of gods. Even their ball court was both religious and bloody, where the losers of the games were killed.