Mohenjo-Daro was an ancient city located in the fertile Indus River Valley, in what is now Pakistan and northwest India. This was one of the most fertile region in the world at the time, with plentiful farm products and animals. The region was surrounded in the north by the Himalayas, protected to the west by the Indu Kush mountains, and insulated from the east by the Great Indian Desert. Like Egypt, this region had unique geographic protections against invasion by foreign enemies. The other ancient city there was Harappa.
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.