Teotihuacan covers an area of a little over twenty-two square miles. It was built, continuously added to, and occupied from about 100 BC to 550 AD. Somewhere about 550 AD, based on still disputed, sketchy archeological findings, the place was sacked, burnt and mostly abandoned. There is evidence that a period of famine could have resulted in a revolution. This would also account for the evidence of destruction by fire. However, some people continued to live at the site, and others may have come there to worship, until about 750 AD. It was the largest and most populated city/sate in the pre-Columbian Americas, with approximately 125,000 residents at its zenith. Influences from this civilization can be found in almost all cultures of Meso-America.
The enormous architectural complex was built to conduct both administrative and religious activities. It initially dominated the region because the inhabitants controlled the obsidian mines, but the administrative and business (trading) skills of the rulers soon made the culture preeminent. They, no doubt, had a military, but were not, it seems, a dominant military power as were the Aztecs who came along much later, and usurped the culture and prestige of the Teotihuacanos, by claiming ancestry.
The city attained a sophisticated level of urbanization, with streets and blocks dominated by two large, perpendicular roads. The north/south Avenue of the Dead is transected by the East/West Avenue. There was an extensive drainage system, and the apartment buildings had sewage systems.
Here’s a photo of Plaza A of the Avenue of the Dead Complex at the south end of that complex. The total length of the Avenue of the Dead is almost three kilometers.
This plaza is huge, covering almost seven-thousand square meters, and is believed to have been a gathering place for religious ceremonies associated with the Templo de Quetzalcoatl (Pyramid of the Plumed Serpent). Quetzalcoatl was the originator of human activities who created the earth and the four seasons. Here is a photo of several depictions of Quetzalcoatl projecting from the pyramid.
The structure on the right shows some remnants of a top coat of red pigmented plaster. Many of the pyramidal structures and apartment buildings of the complex were decorated with murals. Here is a painted mural of a puma.
The two largest and most impressive pyramids on the site, no doubt built to impress, are the pyramids of the sun and moon.
Those are people on top who have climbed the pyramid of the sun. I did 50 years ago, not this time. The pyramid of the moon is significantly smaller, but still impressive. The pyramid of the moon is at the far north end of the Avenue of the Dead, the sun pyramid is about half way between the north and south ends.
These structures were built up with dirt and adobe, then covered with rocks, cemented into place. The rocks were sheathed with a thick coat of gravel, lime and sand (concrete), and then covered with a thinner, finish coat of lime, sand and red pigment.
This photo shows vestiges of the concrete covering on the back side of the pyramid of the sun. Both of these pyramids, and all the platforms seen in these photos, are thought to have been crowned with temples where religious ceremonies were conducted, including, it is believed, human sacrifice.