Why have the aztec ruins in mexico city not been dug up?

In 1519, the Spanish conquistador Hernán Cortés and 400 of his men marched into the Aztec capital of Tenochtitlan and knew at once they were in a strange and wondrous place. Even before their arrival, the emperor Moctezuma II had sent the Spaniards lavish jewels and fine clothes. He may have believed the Spaniards to be the deity Quetzalcoatl, the “plumed serpent,” returning to Tenochtitlan from the east, or he may have thought he was receiving emissaries from a friendly state. According to their own accounts, as the Spaniards began to explore the city, they found temples soaked with blood and human hearts being burned in ceramic braziers. So thick was the stench of human flesh, wrote chronicler Bernal Díaz del Castillo, that the scene brought to mind a Castilian slaughterhouse.HOPE THIS HELPS

In 1519, the Spanish conquistador Hernán Cortés and 400 of his men marched into the Aztec capital of Tenochtitlan and knew at once they were in a strange and wondrous place. Even before their arrival, the emperor Moctezuma II had sent the Spaniards lavish jewels and fine clothes. So thick was the stench of human flesh, wrote chronicler Bernal Díaz del Castillo, that the scene brought to mind a Castilian slaughterhouse.