The Tower of Babel: Outside The Bible
In addition, there is a specific time duration in which this tower must have been built. Archaeological evidence proves that such a ziggurat must have been built no later than 2,400 BC:
‘We see then that the archaeological facts coalesce around the dates 3500 to 3000 B.C. The building of a city not just a settlement, the use of baked brick, the use of bitumen for mortar and the fact that a ziggurat is being built all dovetail in date. This remarkable agreement makes it highly probable that the earliest date to which we can ascribe the tower of Babel as described in Gen 11:1-9 is c. 3500 to 3000 B.C.
But, what is the latest date to which we can ascribe its building? There is a text saying that Sharkalisharri restored the temple-tower at Babylon c. 2250 B.C., and another text indicates that Sargon I destroyed Babylon c. 2350 B.C. 
This suggests that there was a city established at Babylon efore 2350 B.C.; so, allowing a modest 50 years of city history, we can set 2400 B.C. as the terminus ante quem for the first ziggurat built in Babylon. 
We can thus date the building of the tower of Babel sometime between 3500 and 2400 BC.
 CAH3 1:1:219; Evelyn Klengel-Brandt, “Babylon,” OEANE 1:254.
 Ziggurats began as elevated temples and did not become “true ziggurats” until c. 2100 B.c., after which they continued to be built or at least rebuilt until the fall of Babylon in the sixth century B.C.’
Paul H Seely, ‘The Date Of The Tower Of Babel And Some Theological Implications’, page 19, originally published in Westminster Theological Journal 63 (2001) 15-38
This detail provides evidence that the Biblical record of the tower of Babel must itself be very old. Many modern scholars (especially secular academics), wish to argue that the Pentateuch was written at a very late date, supposedly during the Babylonian captivity (6th century BC), though incorporating some earlier material from no earlier than the 10th century BC.
It must be asked how even a 10th century writer living in Israel could possibly have such a precise knowledge of these specific details of religious buildings constructed over 1,400 years before he lived, during a kingdom long since ended, in a geographical area he had never visited. [http://bibleapologetics.wordpress.com/2007/04/]