Gods admonition to the post-flood civilization of man was to go forth and be fruitful and multiply, and replenish the earth (Gen. 8:16-17; 9:1). Then in Genesis ch. 11 we have the people of the earth, rather than spreading out to replenish the earth as God instructed, rallied together and decided to build a tower in the plain of Shinar, that is the location of Nebuchadnezzar's Babylon, or today's Iraq.
"And the whole earth was of one language..." there was a unity in the communication among the early civilization of man. "Let us build us a city and a tower whose top may reach unto heaven; let us make us a name lest we be scattered abroad upon the face of the earth." Had they been scattered, they would have been in obedience to God's command, but instead they incorporated.
When they said "...a tower whose top may reach unto heaven" I see the same boast as in Isaiah 14:13 "For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north"