Towers Were Part of the wall

TOWERS The Oriental city has had two types of towers located in it. First was the tower constructed as a part of the city wall. At this point the wall was built higher and served as a fortification. The approach of an enemy could be sighted from here, and weapons hurled down upon men who attempted to take the city. Almost every gate of any consequence would have a tower over it. Then towers were often built where the wall turned a corner. These were called "corner towers." King Uzziah made use of such towers: "And he made in Jerusalem engines, invented by skilful men, to be on the towers and upon the battlements to shoot arrows and great stones withal" (II Chronicles 26: 15). [Manners And Customs of Bible Lands]