by a.d. 600, this was the most complex society in all of mesoamerica. archaeologist william sanders. in this area where i'm standing, which is right on the southern edge of the ancient city, there are between 80 and 100 permanent springs. there is some convincing evidence that at the time of the peak of the ancient city, the water from these springs was harnessed into an elaborate canal system that provided permanent irrigation for at least 7,000 or 8,000 acres of land down on the bottom of the teotihuacan valley, rich, fertile alluvium with very high productivity. this must have provided at least one of the major sources of the production of staple foods for the ancient city at its peak. keach: some archaeologists think the irrigation system was controlled by the state -- the king and his high-ranking elite -- just as the unidad controls it in cuicatlan today. that control gave the elite enormous power, which can be seen in these massive buildings. man: this is the political center of teotihuacan. the temple of quetzalcoatl behind us represents the pow