Both cities were noted for clear evidence of town planning: regular, broad and straight streets, sophisticated drainage, etc. The cause of their downfall, in about 1500 BC, is unknown. Traditionally it is ascribed to the Aryan invasions of northern India (India and Pakistan); but it may have been caused bu shifts in the course of local rivers causing environmental damage. | Both cities were noted for clear evidence of town planning: regular, broad and straight streets, sophisticated drainage, etc. The cause of their downfall, in about 1500 BC, is unknown. Traditionally it is ascribed to the Aryan invasions of northern India (India and Pakistan); but it may have been caused bu shifts in the course of local rivers causing environmental damage. |