The Indus Valley Civilisation (IVC) was a Bronze Age civilisation (3300–1300 BCE; mature period 2600–1900 BCE) mainly in northwest South Asia, extending from what today is northeast Afghanistan to Pakistan and northwest India. Along with ancient Egypt and Mesopotamia it was one of three early civilisations of the Old World, and of the three the most widespread. It flourished in the basins of the Indus River, one of the major rivers of Asia, and along a system of perennial, mostly monsoon-fed, rivers that once coursed in the vicinity of the seasonal Ghaggar-Hakra river in northwest India and eastern Pakistan. Aridification of this region during the 3rd millennium BCE may have been the initial spur for the urbanisation associated with the civilisation, but eventually also reduced the water supply enough to cause the civilisation's demise, and to scatter its population eastward.