Zócalo is the common name of the main square in central Mexico City. Prior to the colonial period, it was the main ceremonial center in the Aztec city of Tenochtitlan. The plaza used to be known simply as the "Main Square" or "Arms Square", and today its formal name is Plaza de la Constitución. This name does not come from any of the Mexican constitutions that have governed the country but rather from the Cádiz Constitution, which was signed in Spain in the year 1812.