The Indus Valley Civilization flourished in the vast river plains and adjacent regions in what are now Pakistan and western India. The earliest cities became integrated into an extensive urban culture around 4,600 years ago and continued to dominate the region for at least 700 years from 2600 to 1900 B.C. It was only in the 1920's that the buried cities and villages of the Indus valley were recognized by archaeologists as representing an undiscovered civilization.