Mexico City 

Mexico City (Spanish: Ciudad de México) is the name of a megacity located in the Valley of Mexico (Valle de México), a large valley in the high plateaus (altiplano) at the center of Mexico, about 2,240 meters (7,349 feet) above sea-level, surrounded on most sides by volcanoes towering at 4,000 to 5,500 meters (13,000 to 18,000 feet) above sea-level. 

Mexico City was originally a municipality founded in 1521 by Cortés on the ruins of Tenochtitlan, the capital of the Aztec Empire, in the middle of the now drained Lake Texcoco. The municipality was abolished in 1928, and the names “Mexico City” can now refer to two things. 

Officially, the Distrito Federal (D.F.) uses the name Ciudad de México. The D.F. is a federal district serving as the capital of Mexico and which the Mexican Federal Government administers. The D.F. encompasses the historical center of Mexico City, but is much larger than the historical municipality of Mexico City abolished in 1928. The urbanized area of Mexico City covers only the north of the D.F., while the south of the D.F. is made up of rural areas and mountains. Although the D.F. is not a municipality, Mexican authorities use the name Ciudad de México as a synonym for Distrito Federal (such as in Article 44 of the Mexican Constitution). 

In a broader meaning, "Mexico City" refers to the whole metropolitan area of Greater Mexico City. The metropolitan area extends beyond the limits of the D.F. and encompasses tens of independent municipalities located in the State of México (Estado de México), to the north, east, and west of the D.F., extending as far north as the State of Hidalgo. The population of the entire metropolitan area in 2005 is estimated between 18 and 22 million inhabitants (depending where the limits of the metropolitan area are set). This means Mexico City is the third or fourth most populated metropolitan area in the world (behind Tokyo, New York, and possibly Seoul, depending which data is compared). 

Mexico City, with its distinct mestizo culture, blending native Indian (Nahuatl) and Spanish heritages, is the largest metropolitan area in Latin America, and the second largest in the Americas behind New York. By the end of the 20th century it became one of the largest financial, economic, educational, cultural, and tourist centers of the world. 

After centuries of pre-Columbian civilization, Spanish conquistador Hernán Cortés first arrived in the area, then the Aztec capital Tenochtitlan, in 1519. He did not succeed in conquering the city until August 13, 1521, after a 79-day siege that destroyed most of the old Aztec city. 

The city served as the capital of the viceroyalty of New Spain from ca. 1525 to the outbreak of the War of Independence in 1810, and of the various Mexican states afterwards. 

Most of the growth of Mexico City in population occurred in the late 20th century. In 1950 the city had about 3 million inhabitants. By 2000 the estimated population for the city proper was around 18 million.