Sometimes the term also includes the inhabitants of Tenochtitlan's two principal allied city-states, the Acolhuas of Texcoco and the Tepanecs of Tlacopan, who together with the Mexica formed the Aztec Triple Alliance that controlled what is often known as the "Aztec Empire". In other contexts, Aztec may refer to all the various city states and their peoples, who shared large parts of their ethnic history and cultural traits with the Mexica, Acolhua and Tepanecs, and who often also used the Nahuatl language as a lingua franca. In this meaning it is possible to talk about an Aztec civilization including all the particular cultural patterns common for most of the peoples inhabiting Central Mexico in the late postclassic period.
From the 13th century, the Valley of Mexico was the heart of Aztec civilization: here the capital of the Aztec Triple Alliance, the city of Tenochtitlan, was built upon raised islets in Lake Texcoco. The Triple Alliance formed a tributary empire expanding its political hegemony far beyond the Valley of Mexico, conquering other city states throughout Mesoamerica. At its pinnacle, Aztec culture had rich and complex mythological and religious traditions, as well as achieving remarkable architectural and artistic accomplishments. In 1521 Hernán Cortés, along with a large number of Nahuatl speaking indigenous allies, conquered Tenochtitlan and defeated the Aztec Triple Alliance under the leadership of Hueyi Tlatoani Moctezuma II. Subsequently, the Spanish founded the new settlement of Mexico City on the site of the ruined Aztec capital, from where they proceeded with the process of colonizing Central America.