Mexico City Mexico City is the capital of Mexico and the second largest city in the world. About 9 1/3 million people live in Mexico City. Mexico City area size is 579 sq. mi. Mexico City lies 7,525 feet above sea level in the high, oval-shaped Valley of Mexico. Mexico City has more than 350 neighborhood districts called colonias. Like Mexican towns, many colonias have plazas(public squares). Churches, markets, restaurants, and theaters face the plazas. The Mexico City metropolitan area, with about 14 1/2 million people, is the world's largest metropolitan area and its size area is 883 sq. mi. It's the country's commercial and industrial center. Mexico city's metropolitan areas' pollution