Answer:
The answer is Indus Valley civilization.
Explanation:
The Indus valley civilization lasted from 3300 BCE to 1300 BCE, making it one of the oldest and the longest standing civilizations of that era.
The Civilization's cities were know for the superior sanitation systems they had comparatively to the contemporary cities at the time.
Also, it was the Largest civilization out of the 4 main ancient civilizations.
The other 3 were,
-Egyptian civilization
-China's Hwang How Civilization
-Euphrates and Tigris civilization in Mesopotamia
