Indus Valley had reached its full development in 2300 BCE and began to disintegrate
some 500 years later. It was essentially urban and mercantile. There seems to have been
no dominant class of priests or warrior, both in Harappa and Mohenjo-daro. The cities were regularly planned with wide streets for traffic. Pipe fresh water and drains
were systemically provided. There were no fortifications. Each had a citadel raised on an
artificial mud-brick mound, like ziggurat but all building were built of fire-burnt brick