Copilco

Under the houses of Copilco el Bajo, in Coyoacán, lies a village more than 2,500 years old. People lived here on the edge of the Pedregal in the Middle Preclassic, roughly 800 to 200 BC, and successive eruptions buried what they left. The last and thickest came from Xitle about 1,670 years ago and laid some five metres of basalt over the site. Recent INAH and UNAM work also found an older ash, the so-called Black Tephra from a different eruption, and dated charcoal from the busiest occupation layer to around 840–780 BC. The dead were buried in bell-shaped pits cut into the tepetate, under or beside the houses, with pottery, figurines and grinding stones.

In August 1917 Manuel Gamio picked the Copilco quarry, out of every working quarry in Coyoacán and San Ángel, to pin down the so-called Archaic culture, then the oldest known in the Basin of Mexico. His workers drove tunnels beneath the lava, and late that November a complete skeleton turned up, the "man of the Pedregal", which made the front pages. Alfred Kroeber dug here again in 1924.

In 1918 the tunnels became one of the first site museums in Mexico. Its three rooms covered the geology of the Pedregal, burials left in place under glass, and a pottery sequence running from Aztec sherds on top of the lava to Archaic ones beneath it. By the 1960s it was a stop on a south-side circuit with Ciudad Universitaria and Cuicuilco. In the early 1980s it was closed to the public because the tunnels were unstable and the bones were deteriorating, and INAH archaeologists resumed research in 2012. It is not open to visitors.