The national capital is Mexico City, situated in the heart of central Mexico. In pre-Columbian times it was the site of the capital of the Aztec Empire and during the three centuries of colonial rule it was the seat of the viceroys of New Spain. Mexico City today is the second largest city in the world with 17 million inhabitants as of 1995. Most administrative and economic activities are concentrated in Mexico City. A ring of cities—Puebla, Cuernavaca, Toluca, and Querétaro—surrounds the capital. Other major cities are Guadalajara in the west and the industrial city of Monterrey in the north. In the late twentieth