Mohenjo-daro did not have city walls but was fortified with watchtowers west of the main settlement and defensive fortifications to the south.

It is presumed, given the fortifications and structure of the other major cities of the Indus Valley, that Mohenjo-daro served as the administrative center. Both Mohenjo-daro and Harappa are built similarly, have a similar architectural layout, and both cities were not heavily fortified compared to other towns in the valley. Perhaps their function was different.