This is for Majesty

It's funny how when something you never really think about comes up, it continues to come up repeatedly for a while. I was reading the Scientific American on ancient civilisations and what do they chose to point out as one of the shining accomplishments of the ancient Indus Valley city of Harappa (which peaked between 2600 B.C. and 1900 B.C.)?

Harappan houses were equipped with bathing areas, latrines and sewage drains. Linked to larger mains, which eventually emptied outside the city walls, the sewers at Harappa would have removed waste-water from the habitation areas, depositing fertile sludge on the surrounding agricultural fields.