The Aztecs were an Indian empire of central Mexico that reigned during the 14th, 15th, and 16th centuries. With a civilization that numbered as many as six million people, the Aztecs were masters of agriculture, irrigation, engineering, and astronomy. The Aztecs were also a military force and spread through Mexico by conquering neighboring tribes. Many of the conquered were later sacrificed to appease the Gods.

In 1521, Spanish explorer Hernando Cortes and his army suceeded in conquering the Aztecs after a long struggle. The beautiful Aztec capital, Tenochtitlan, which was once full of dazzling metals and jewels, was all but destroyed. Mexico City was soon built atop the ruins.

Today, Mexico City is one of the world's largest, busiest, and most polluted city. In 1970, the ruins of Templo Mayor, or, Great Pyramid, were excavated after being discovered by subway workers. The 197 feet high temple was once the primary site of worship in Tenochtitlan. It was surmounted by shrines to the Aztec God of war and sun Huitzilopochtli, and the God of Fertility and Rain, Tlaloc.