 The top tower along the front wall of the forward compound , tower 6 , has a square base which was reinforced with a six @-@ sided foundation . Working west , the square base of tower 7 was reinforced with a circular foundation . Tower 8 , on the upper side of the front portcullis , has an irregular , but generally square , base . It is also the shortest of the first nine towers . Guarding the other side is tower 9 , which has a square base reinforced by an eight @-@ sided foundation . 
