Indus Valley Civilization The earliest known Southern Asian civilization, flourishing c.2300- 1750 BC across 1.1 million km2 / ½ million mi.2 around the Indus in Pakistan. Over 100 sites have been identified with important urban centers at Mohenjo-daro and Harappa (Pakistan), and Kalibangan and Lothal (Western India). There were uniform principles of urban planning, with streets set out in a grid pattern and public drainage systems. Weights and measures were standardized, and there was widespread trade with Western Asia. A common writing system was used, which remains undeciphered. Great granaries on citadel mounts suggest the existence of priest-kings or a priestly oligar