Teotihuacán arose in the high basin of central Mexico and grew into one of the largest cities of the ancient Americas. Settlement expanded during the last centuries BCE, perhaps drawing people displaced by volcanic activity and political change elsewhere in the basin. By the first centuries CE, planners had established a monumental north-south avenue later called the Avenue of the Dead. The city’s ancient name and the languages spoken by its diverse inhabitants remain uncertain; Teotihuacán is the much later Nahuatl name used by the Mexica, or Aztecs.

The Pyramid of the Sun was built around the second century CE over a cave and earlier sacred features. The Pyramid of the Moon anchored the avenue’s northern end against Cerro Gordo, while the Ciudadela enclosed the Temple of the Feathered Serpent. That temple’s sculpted facade and mass burials reveal close links between religion, warfare, and state authority. Monumental construction required enormous quantities of stone, lime plaster, timber, food, and organized labor. Brightly painted surfaces would have made the ancient city far more colorful than the exposed masonry visible today.

Teotihuacán was also a city of residential compounds, workshops, markets, murals, and immigrant neighborhoods. Apartment compounds housed extended groups with shared courtyards and shrines. Artisans produced obsidian blades, ceramics, ornaments, and ritual objects for local use and long-distance exchange. Evidence from Oaxaca, the Gulf Coast, and Maya regions shows that outsiders lived in the city, while Teotihuacán’s imagery and political influence reached across Mesoamerica. Its population may have exceeded one hundred thousand at its height, though estimates remain debated.

During the sixth century, parts of the ceremonial center were burned and political authority fractured. Environmental stress, inequality, internal conflict, and changing trade networks have all been proposed as causes; no single explanation has resolved the decline. Occupation continued on a smaller scale, and later societies treated the ruins as a sacred landscape. Mexica traditions connected the site with the creation of the sun and moon, and rulers visited it before the Spanish conquest. The pyramids thus acquired new meanings centuries after the original city had lost its power.

Modern excavation began in the nineteenth century and intensified around the centennial of Mexican independence in 1910, when large-scale reconstruction reshaped the Pyramid of the Sun. Later projects uncovered murals, offerings, tunnels, burials, and evidence of everyday life, while conservation addressed unstable plaster and heavy visitation. Mexico’s National Institute of Anthropology and History manages the archaeological zone and its museums, and UNESCO inscribed it in 1987. Teotihuacán’s value rests on the whole urban system: monuments, neighborhoods, infrastructure, production, migration, and sacred geography together document an unusually influential experiment in ancient city life.