The Aztecs were a highly advanced civilization that developed in the 1427 around the area that is now called Mexico City. They established a massive empire that ran a course of approximately 200 years and engaged in a variety of military and tribute conquests. The Aztec Empire was a triple alliance between the city-states Tlacopan, Texcoco and Tenochtitlan. They choose an uninhabited island in Lake Tetxcoco. Which was then called Tenochtitlan. At this location they ended up being surrounded by their enemies. It featured a huge temple complex, a royal palace, and numerous canals. The site turned out to be a strategic location, with abundant food supplies and waterways for transportation. Tenochtitlan was mainly in charge of the military and conquests, whereas the other two cities had other responsibilities. The Aztec built great cities and developed a complex social, political, and religious structure. Aztec society was highly structured, based on agriculture, and guided by a religion that pervaded every aspect of life. Aztec art was primarily an expression of religion, and even warfare, which increased the empires wealth and power, served the religious purpose of providing captives to be sacrificed.