In 1519, when the first Spaniards marched into the city of Tenochtitlán, it was the heart of the Aztec empire. Founded on a lake island in 1325, the city was the nerve center of political and economic control of an extensive area of Native America. More than 200,000 people lived in an urban area measuring almost 15 square kilometers, which included approximately 80 civil and religious buildings. The most important of these was the Templo Mayor, or Main Temple, on the crest of which were found two shrines; one dedicated to the god of war Huizilopochtli, and the other to the rain god Tláloc. Today, you can still see the temple’s pyramidal base, enlarged seven times in 200 years. To one side of the site is the Casa de los Caballeros Aguila, House of the Men-Eagle, which once housed an ancient order of elite warriors.