Teotihuacan, Pyramid of the Moon, from the Pyramid of the Sun

Teotihuacan was an ancient Mesoamerican city located in a sub valley of the Valley of Mexico, located in the State of Mexico near modern-day Mexico City, known today as the site of many of the most architecturally significant Mesoamerican pyramids built in the pre-Columbian Americas. Apart from the pyramids, Teotihuacan is also anthropologically significant for its complex, multi-family residential compounds; the Avenue of the Dead; and the small portion of its vibrant murals that have been exceptionally well-preserved. Additionally, Teotihuacan exported fine obsidian tools that garnered high prestige and widespread utilization throughout Mesoamerica.

The city is thought to have been established around 100 BC, with major monuments continuously under construction until about AD 250. The city may have lasted until sometime between the 7th and 8th centuries AD, but its major monuments were sacked and systematically burned around 550 AD. At its zenith, perhaps in the first half of the 1st millennium AD, Teotihuacan was the largest city in the pre-Columbian Americas, with a population estimated at 125,000 or more, making it at least the sixth largest city in the world during its epoch. Teotihuacan was even home to multi-floor apartment compounds built to accommodate this large population. The term Teotihuacan (or Teotihuacano) is also used for the whole civilization and cultural complex associated with the site.

Although it is a subject of debate whether Teotihuacan was the center of a state empire, its influence throughout Mesoamerica is well documented; evidence of Teotihuacano presence can be seen at numerous sites in Veracruz and the Maya region. The later Aztecs saw these magnificent ruins and claimed a common ancestry with the teotihuacanos, modifying and adopting aspects of their culture. The ethnicity of the inhabitants of Teotihuacan is also a subject of debate. Possible candidates are the Nahua, Otomi, or Totonac ethnic groups. Scholars have also suggested that Teotihuacan was a multi-ethnic state.

The site covers a total surface area of 83 square kilometres and was designated a UNESCO World Heritage Site in 1987. It is the most visited archaeological site in Mexico.

The Pyramid of the Moon is the second largest pyramid in Teotihuacan, after the Pyramid of the Sun. It mimics the contours of the mountain Cerro Gordo, just north of the site. Some have called it Tenan, which in Nahuatl, means "mother or protective stone." The Pyramid of the Moon covers a structure older than the Pyramid of the Sun which existed prior to 200 AD.

The Pyramid's construction between 200 and 450 AD completed the bilateral symmetry of the temple complex. A slope in front of the staircase gives access to the Avenue of the Dead, a platform atop the pyramid was used to conduct ceremonies in honor of the Great Goddess of Teotihuacan, the goddess of water, fertility, the earth, and even creation itself. This platform and the sculpture found at the pyramid's bottom are thus dedicated to The Great Goddess.

Opposite the Great Goddess's altar is the Plaza of the Moon. The Plaza contains a central altar and an original construction with internal divisions, consisting of four rectangular and diagonal bodies that formed what is known as the "Teotihuacan Cross."