The Historic Center or Centro Histórico lies at the central neighborhood of Mexico City. This includes the Zócalo or the main plaza and extends in all directions covering a total of about 4 hectares. The Historic Center has been both the center of the ancient Aztec Empire known as Tenochtitlan and the seat of power for the Spanish colony of New Spain. Most of the city’s historic sites from both eras can be seen in this part of Mexico City with 1,550 buildings declared as historically important. It was therefore recognized as a World Heritage Site because of the area’s cultural and historical value.