FIRST, it began a project that had been planned several years earlier: the excavation of the Great Temple. Second, it helped us set some precedents in Mexican archaeologyfor example, not to reconstruct a building if its destruction is historical fact. But this discovery also helped us in our search for answers to still unsolved questions, for the Great Temple was symbolically the seat of Aztec power. The presence of Tlaloc and Huitzilopochtli, gods of rain and war, at the top of the temple shows us the economic base of the empire: water for agricultural production, and war as a means of obtaining tribute from subject territories. War also supplied captives to offer in sacrifice to the gods. Yet beyond that significance, the temple represents one of the most important Aztec myths: the birth and battles of the tribal god Huitzilopochtli. The myth of a battle between Huitzilopochtli and his sister Coyolxauhqui probably springs from an actual event. Nahuatl literature recounts how Huitzilopochtli incited his people to leave their Aztlan homeland under his leadership. A quarrel between two groups occurred at Coatepec, or “serpent hill”: One group was headed by Huitzilopochtli, the other by his many brothers, collectively called the Huitznahua (weets-NAH-wah), and his sister Coyolxauhqui. In the ensuing power struggle, Huitzilopochtli prevailed. It is significant that one of the barrios of the Aztec capital, Tenochtitlan, later bore the name of the Huitznahua, which indicates that despite their defeat in that squabble, the group still had exalted status within tribal society. Ghost of the past, a drawing of the Great Temple looms over its ruins in an aerial photograph of downtown Mexico City (right). Beyond sprawls the cathedral and the vast square of the Scale. To the rear of the temple, foreground, excavations reveal the foundations of smaller pyramids. Archaeologists razed stores, rooming houses, and a city street to bare the Great Temple site. The Charcoal (left), a figure originally associated with the Toltec culture, was unearthed in the oldest structure found. An archaeologist measures the crude carving, the first found with its original color.