Genesis 11:4

Genesis 11:4
Under Nimrod's leadership the people of that day started building a city so as to stay together rather than spread over the Earth as God had commanded. They also started to build a tower that as to be a center of worship. The reference to the reaching unto heaven may have just have been a reference to it being so high that it towered over the rest of the city, it may have been a purely figurative reference to worship, it may have severed to an observatory of the star.