Genesis 11:2

And it came to pass, as they journeyed from the east, that they found a plain in the land of Shinar; and they dwelt there. From the highlands of the Ararat range the survivors of the Flood and their families moved down, by degrees, in an easterly direction until they reached the great plain where the Euphrates and Tigris rivers flow. It is a rich and fertile plain, or was in those days, and the people were constrained to give up their nomadic form of living and establish permanent sites for homes.