Mohenjo-daro

Mohenjo-daro ("Mound of the Dead Men" in Sindhi) was, at its height around 2500 BCE, one of the largest cities of the Indus Valley Civilization (also called the Harappan Civilization), with an estimated population of up to 40,000 people living in a city laid out on a precise grid of streets oriented to the cardinal directions, with standardised baked-brick houses connected to one of the world's earliest known urban sanitation systems — covered drains running beneath most streets, centuries before comparable systems appeared elsewhere. The Indus script found on seals throughout the site remains undeciphered, meaning the civilisation's own names for itself, its rulers, and its gods are unknown to us.

The civilisation went into decline around 1900 BCE, and Mohenjo-daro was abandoned by around 1700 BCE; mainstream archaeology attributes this to a combination of factors including the shifting course of the Indus river system, prolonged drought linked to the weakening of monsoon patterns, and the resulting collapse of the agricultural surplus that had sustained the cities. In the 1970s, the discovery of scattered, unburied human skeletons in the upper levels of the site — interpreted by some early excavators as evidence of a final massacre — fed a fringe theory, popularised from the 1960s onward, that the city had been destroyed by an ancient nuclear explosion, citing reports of fused, glassy material ("black stones") at the site as evidence of intense heat. Mainstream archaeologists have rejected this interpretation, noting that the skeletons date to different periods spanning the city's decline rather than a single event, and that the "glassy" material is consistent with ordinary kiln slag from the site's brick- and pottery-making industries.