Teotihuacán, to the North of México City, arose around the time of Christ, and quickly became the largest and most populous urban centre in the New World. It rapidly expanded to cover an area of 20 square km with 80,000 inhabitants . By the fourth century, it was the sixth largest city in the World and during its period of greatest prosperity, had an estimated population of 125,000.
The city functioned for centuries until its rather sudden collapse, probably in the seventh century. The place was called Teotihuacán by Nahuatl speakers several centuries after the City's fall, but its original name, the language or languages spoken there, and the ethnic groups who built the City are still unknown. It remains a mystery to this day. 
The Important Cities and Cultures of Ancient MesoAmerica - including Teotihuachán
Panoramic view of the enormous Sun Pyramid
With its 2 Great Pyramids of the Sun and the Moon, the City
is easily as impressive as the Ancient Egyptian site at Giza, and strangely, even though the 2 Ancient Cultures did not know of each others existence, the Great Pyramid at Giza and the Sun Pyramid at Teotihuachán have a similar footprint in terms of their dimensions at the base. Originally the Sun Pyramid was approximately 215 by 215m at the base, and about 63 m high. It was significantly enlarged at least twice in later periods, resulting in a final size of 225m along each side. The Pyramid is located on the east side of the main street - The Avenue of the Dead in the northern half of the city. The importance of the Pyramid is indicated by a cave located under the structure. It is believed that the cave was used for rituals.
Climbing the Sun Pyramid with the Moon Pyramid behind
The Pyramid of the Moon is located at the extreme northern end of the Avenue
of the Dead, the principal axis of the city of Teotihuacán. Facing towards the south, it was constructed as the principal monument of the Plaza of the Moon. For many years it was believed that the Pyramid contained earlier structures within its walls, but until the Pyramid of the Moon Project excavations began in 1998, archaeologists could only guess at how many there were and how they had been constructed. Over the last decade, as a result of the fieldwork that has been carried out, a large quantity of information and materials have been obtained. See below for my photos of some of the fascinating finds from these recent excavations. It was a common practice when burying someone of importance to sacrifice a couple of honoured victims to accompany them on their journey to the afterlife, and the Pyramid of the Moon was no different.
The Pyramid of the MoonSee Palenque's tomb of
The Red Queen for another example of this practice. You can see carved obsidian objects as well as the skeletons of animals, including jaguars, all found inside the Pyramid of the Moon.