'Tower' in the Bible

Or those eighteen who were killed when the tower in Siloam fell on them, do you think they were worse offenders than all the others who live in Jerusalem?

For which of you, wanting to build a tower, doesn't sit down first and compute the cost to see if he has enough money to complete it?

Otherwise, when he has laid a foundation and is not able to finish the tower, all who see it will begin to make fun of him.