‘And the beginning (or ‘chief part' or ‘mainstay' - reshith - compare the use in Jeremiah 49:35 - ‘the chief' of their might) of his kingdom was Babel and Erech and Accad and Calneh in the land of Shinar. Out of that land he went forth into Assyria and built Nineveh and Rehoboth-Ir and Calah, and Resen between Nineveh and Calah (the same is the great city).'
Shinar is Babylonia proper (Hittite - Shanhar - see Genesis 11:2; Genesis 14:1; Isaiah 11:11; Daniel 1:2; Zechariah 5:11), Babel is Babylon, Erech is Uruk, a very ancient city (the city where Gilgamesh, of the Gilgamesh epic, reigned, now modern Warka), Accad is Akkad or Agade, which ruled a great empire prior to the time of Abraham - site unknown. Calneh is less certain but may be connected with the Kullania mentioned in Assyrian tribute lists. Alternately it may mean ‘all of them' (Hebrew kullana) i.e. all the others.
Nineveh is Nineveh, Calah is Kalhu (modern Tell Nimrud) on the bank of the Tigris twenty four miles south of Nineveh. Rehoboth-Ir and Resen are unknown. However, resen goes back to Akkadian res eni meaning ‘head of a spring', a common Assyrian place name. Rehoboth Ir could relate to Akkadian rebatu alu which parallels Sumerian as.ur, referring to Ashur.
The differentiation between the cities he ‘built' and the earlier cities may suggest that he obtained the former by conquest. Indeed even the ‘building' could be rebuilding and fortifying. Thus we may well see Nimrod as coming up from Africa on a trail of conquest and settling in Mesopotamia to found an empire. Elsewhere in Sumerian, Assyrian and other records he was seen as a legendary figure performing great exploits. It is possible that he was the source from which came the idea of Ninurta (Nimurda) the Babylonian and Assyrian god of war.
“The same is the great city”. This may refer to the four cities as being seen as forming one great metropolis stressing the greatness of his empire.
Connecting these facts with Genesis 11:2 may suggest that it was Nimrod who was responsible for that debacle (but then we might expect a mention here - compare Genesis 10:25), but it is more probable that it occurred before Nimrod's time. Certainly this mention of Nimrod is ominous as it is the first mention of empire building and conquest in the record in Genesis 1-11. What the world would no doubt see as a glorious triumph is anathema to God, as chapter 11 makes clear.