The Aztecs were a Pre-Columbian Mesoamerican people of central Mexico in the 14th, 15th and 16th centuries. They called themselves Mexica. The Republic of Mexico and its capital, Mexico City, derive their names from the word "Mexica".
The capital of the Aztec empire was Tenochtitlan, built on raised island in Lake Texcoco. Mexico City is built on the ruins of Tenochtitlan. The Spanish colonization of the Americas reached the mainland during the reign of Huey Tlatoani , Moctezuma II (Montezuma II). In 1521 Hernan Cortes and an allied army of American Indians that far outnumbered the defending Aztecs, conquered the Aztecs through germ warfare, siege warfare, psychological warfare, and direct combat.
According to their own history, when the Mexicas arrived in the Anahuac valley (Valley of Mexico) around Lake Texcoco, the groups living there considered them uncivilized. The Mexicas borrowed much of their culture from the ancient Toltec whom they seem to have at least partially confused with the more ancient civilization of Teotihuacan. To the Mexicas, the Toltecs were the originators of all culture; "Toltecayotl" was a synonym for culture. Mexica legends identify the Toltecs and the cult of Quetzalcoatl with the mythical city of Tollan, which they also identified with the more ancient Teotihuacan.
The center of the Aztec civilization was the Valley of Mexico, a huge, oval basin about 7,500 feet above sea level. The Aztec empire included many cities and towns, especially in the Valley of Mexico. The largest city in the empire was the capital, Tenochtitlan.