A tunnel found sealed beneath one of Teotihuacan's pyramids in this century turned out to hold liquid mercury and thousands of buried offerings.
The two great pyramids
The Pyramid of the Sun and the smaller Pyramid of the Moon anchor the city along the Avenue of the Dead, a name given by the later Aztecs, who found the city already ancient and abandoned when they encountered it and mistook its platforms for tombs.
What the Feathered Serpent Pyramid hid
Beneath the Temple of the Feathered Serpent, archaeologist Sergio Gomez located a sealed tunnel in 2003 and spent over a decade excavating it. Finds included pools of liquid mercury, thousands of finely worked objects in jade and obsidian, sculpted figures, and organic remains, all interpreted as a deliberately assembled offering, with some researchers proposing the tunnel's deepest chamber may have functioned as a symbolic entrance to the underworld or even held a ruler's remains, though no confirmed royal burial has yet been announced.
Bound captives at the pyramid's base
Earlier excavations of the same pyramid's foundations found more than a hundred sacrificial burials, many of the individuals bound and accompanied by weapons or warrior-associated ornaments, suggesting captives, possibly from rival polities, killed to consecrate the structure at its dedication, a practice that argues for organised state violence at the heart of the city's foundational ritual.