The Aztecs were among the ancient peoples who inhabited Mesoamerica. They relied on both military conquest and diplomatic alliances to expand their empire (1)---- it grew into one of the largest in pre-Columbian history. Expansion accelerated dramatically under the reign of Moctezuma I beginning around 1440. Moctezuma and his successors built an extensive tributary system made up of numerous city-states, each (2)---- by a local governor loyal to the empire. Following every new conquest, elaborate causeways, many of which crossed lakes, were built to connect it to the capital of Tenochtitlan and the rest of the empire. With its remarkable engineering, the Great Temple is the best-preserved (3)---- of Aztec civilisation. It remains today a fine example of architecture and urban planning, (4)---- being largely destroyed following the Spanish conquest in the 16th century. The scale of the stonework, the elevated position of the temple complex, and the numerous shrines identified among its ruins all seem to indicate that the site was profoundly important (5)---- the Aztec people.