In the heart of the Oaxaca valley in what is today Mexico, the Zapotecs founded a series of urban centers. Mitla was one of the most significant of these – a metropolis that, when the Spanish took it over in the 16th century, had nearly half a million residents, a solar calendar as well as a separate calendar for ritual purposes, its own writing system, and a thriving agricultural production of squash, chili peppers, maize and beans. In the dry Oaxaca valley, the Zapotec had organized irrigation systems, fortifications, and built impressive religious and cultural structures, surviving despite the occasional incursions of neighboring Mesoamerican groups. They would survive Spanish conquest, too: there are still nearly a million Zapotec in Mexico today.

The name "Mitla" is a Spanish gloss of the Nahuatl word meaning "place of the dead." And the dead of Mitla were an auspicious group. Zapotec religion divided the living and the dead into two distinct categories, each with their own gods; to be buried at Mitla meant that the dead would become fused not with the gods of death, but with the gods of the living – Lightning and Earthquake. These lucky nobles became "cloud people," living on in the skies to help their descendants.

While the Spanish plundered Mitla and sought to erase it as a religious and cultural center for the Zapotec, the climate has preserved what they left. Most significant are Mitla’s grecas – carvings in the walls of its stone plazas. These have dizzying geometrical patterns, suggesting the scales of a giant serpent (a mythological creature in Mesoamerican legend) which, during Mitla’s height, would have been painted a deep red.