The Templo Mayor Museum exists because of a 1978 electricity cable. Workers digging near the Zócalo unearthed a massive stone disc depicting the dismembered goddess Coyolxauhqui, thrown from a mountain by her brother, the war god Huitzilopochtli, according to Aztec cosmology. The find forced an awkward question: what else was down there?

The answer, it turned out, was the sacred heart of the Aztec empire. The great temple of Tenochtitlán, destroyed and buried under colonial buildings since 1521, had been hiding beneath Mexico City for four and a half centuries. Excavations uncovered seven construction stages and artefacts from across the empire, all now housed in the adjacent museum.

VoiceMap's self-guided audio tours use the museum and its ruins to trace how a city erased another city, explaining why the Aztecs built in layers, what the Coyolxauhqui stone meant, and why it took four centuries to dig it up.