The whole world had one language and everyone was able to communicate with each other. As they moved toward the east they wanted to build a city in a plain they had settled in.
Let us make a city
The people decided that they wanted to build a tower to the heavens in order to make a name for themselves so that they could stay together.
The Lord came down to see the city and the tower, and "The Lord said, “If as one people speaking the same language they have begun to do this, then nothing they plan to do will be impossible for them. Come, let us go down and confuse their language so they will not understand each other.”" (Genesis 11:6-8)