The Indus Valley Civilization was located in the floodplain of the Indus and Suwarti Rivers, and it was about the best place in the world to have an ancient civilization, because the rivers flooded very reliably twice a year, which meant that it had the most available calories per acre of pretty much anywhere on the planet. We know the Indus Valley Civilization flourished a long time ago, probably around 3000 BCE. Why is that question literally hanging over my head? But people of the Indus Valley were trading with Mesopotamians as early as 3500 BCE. We also know that it was the largest of the ancient civilizations. Archaeologists have discovered more than 1500 sites. So what do we know about this civilization?