What civilization built cities at harappa and mohenjo dark and built a sanitation system

Harappa was, in fact, such a rich discovery that the Indus Valley Civilization is also called the Harappan civilization. The first artifact uncovered in Harappa was a unique stone seal carved with a unicorn and an inscription.

I believe someone else has answered this question but correct me if I'm wrong, it was the Indus Valley Egypt Mespotamia China