Indus Valley civilization
The Indus Valley civilization, also known as the Harappan Civilisation, was a Bronze Age civilization centered on the valley of the Indus River in northwestern South Asia. It flourished from around 2500 BC to around 1500 BC, although exact dates are disputed.
The causes of its decline are controversial. It is associated with invasions / migrations by Indo-Europeans, but causes such as climate changes have also been proposed as (partial) explanations.