Question:
How did the tower of Babel get built, since they did not know their own languages?

Answer:
The account of the building of the tower of Babel (see Genesis 11:1-9) leaves one uncertain as to whether or not they actually finished the tower. In verse six the Lord says, “…and this they BEGIN TO DO,” implying that it wasn’t finished. We know from verse seven that the Lord confounded their language (gave them different languages) so that they would be scattered upon the face of the earth (vs. 8, 9). We know from Genesis 9:1 that God had given Noah the commandment to replenish (fill up) the earth, and the people building the city and tower were disobeying that commandment (see v. 4). Thus, the giving of languages was used by God to destroy their purpose and to accomplish His.