Mexico City is Mexico's capital and the newest of the 32 states of Mexico. Prior to receiving statehood in 2016 it was also known as the Distrito Federal or D.F.The city center is built on the ruins of the Aztec capital Tenochtitlan, and later came to be the capital of New Spain, which included much of North America.
The city has grown fast in the 20th century, and is today North America's largest city (and the world's largest Spanish-speaking city) with 8.9 million inhabitants in the city proper, and more than 20 million in the urban area. The greater Mexico City metropolitan area is one of the world's largest and the largest city in North America, with a 20.1 million people living in the metropolitan area as of the 2010 census. It is situated in the Valley of Mexico and shaped roughly like an oval of about 60 km by 40 km with large parts of it built on the dry bed of Lake Texcoco, and surrounded on three sides by tall mountains and volcanoes such as the Ajusco, the Popocatepetl and the Iztaccihuatl.
Legally and practically speaking, Mexico City refers to the city proper and is the area where tourists will spend all or most of their time.