Nobody knows what the builders of Teotihuacan called the Pyramid of the Sun; the Aztecs named it after arriving centuries after the city was abandoned. Standing on the Avenue of the Dead between the Pyramid of the Moon and the Ciudadela in modern Mexico, it is the third largest ancient pyramid in the Americas after La Danta in Guatemala and the Great Pyramid of Cholula. Its base measures roughly 220 by 230 meters and it holds over 1.18 million cubic meters of material, most of it raised in one phase around 200 AD by workers carrying earth and volcanic rock in tumpline baskets into a grid of internal retaining walls. Surveys list its height as either 65.5 or 71.17 meters, depending on whether the vanished summit temple is counted.

The pyramid was once coated in lime plaster, which required burning huge amounts of wood and served as waterproofing, and painted with jaguars, stars, and snake rattles. It aligns north with Cerro Gordo and with sunrises and sunsets on Mesoamerican quarter days, and the city grid copies its orientation. In 1971 archaeologist Ernesto Taboada found a seven meter pit at the foot of the stairs leading to a cave under the pyramid’s center, once proposed as Chicomoztoc, the Nahua cave of origins. Doris Heyden argued the underground shrine came first. Rene Millon’s 1959 tunnel study found pottery and hearths, and the craftsmanship and immigrant neighborhoods argue against the idea that slaves built it.

• The missing summit altar, which leaves the deity once worshipped at the top unknown
• Why caves were seen as wombs of the earth tied to Tlaloc and rain festivals like Etzalcualiztli
• Obsidian arrowheads and human figurines found inside, thought to represent sacrificial victims
• The stone Teotihuacan Ocelot container found near the pyramid, now in the British Museum
• Child burials at the corners as dedication offerings, and muon detectors now scanning for hidden chambers