Under Mexico City, Hidden Cultures
Under the Historic Center of Mexico City lies what was once Tenochtitlan, capital of the Aztec Empire.
As I walk along the public squares, buildings, churches, museums and markets in the Historic Center of Mexico City I cannot help thinking that under my feet are still remnants of what once was the capital of the Aztec Empire. That amazing city that was destroyed during the Spanish conquest and rebuilt as The New Spain.
“Among us there were soldiers who had been in many parts of the world, and in Constantinople, and throughout Italy and Rome, and said so Compans Square concert with both size and full of so many people had not seen.” Bernal Diaz del Castillo
It was first thought that the Temple was under the Cathedral but after investigation was discovered that it was elsewhere, the modern-day archeological site lies just to the northeast of the Zocalo, or main plaza of Mexico City, on the corner of what are now Seminario and Justo Sierra streets. 
At the Aztec ruins you can see part of the Metropolitan Cathedral where the Temple was previously believed to be under.
Representation of Quetzalcoatl, the plumed serpent, found during excavations.
The archaeological site was discovered on February 21, 1987, by a group of employees of the company Luz y Fuerza del Centro, which carried out excavations in order to place underground wiring. Lowering the floor level one of the workers hit a circular stone relief, and called the department of archeology. The stone was a representation of the goddess of the moon (Coyolxauhqui). 
Buildings and a vacant lot under the temple was found.
People continued living and walking around the city for years without suspicion, we know that Hernán Cortés used material from the ruins after the Conquest to build the New Spain, although there is only one part of the Temple you can still see part of its architecture and there have been found a lot of Aztec art, figures, jewelry, gifts, deities and even the area of the temple where human sacrifices were carried out has been identified .
Excavation and discovery of Tenochtitlan.
A model representation of the Templo Mayor.
The Temple was rebuilt seven times by different Aztecs rulers, building on top of preview layers. There were several reasons to build so many layers of the temple but one of the most important was to prevent the constant flooding that since then has affected the Valley of Mexico.
What you can see today. A city under another.
Not only were things of the Aztec civilization found, but also remains from the Viceroyalty of Spain, crafts, jewelry, religious images, and even part of the architecture of that time, such as the six foot wide aqueduct that crossed the Templo Mayor .
It continues to amaze me that there is one city over another, houses, museums and buildings on ceremonial centers and figures representing Aztec deities, temples under churches, a culture completely covering up another.
Great Temple Museum