One of the greatest rulers of the Arab Caliphate  Abu Jafar al-Mansur, who constructed the city of Baghdad, erected around the defensive wall, account four angles of 90 degrees and four gates (Mu’adham, Dhafariya (Wastani), Halaba, Basaliya). To date, only preserved gate Wastani. It is a high cylinder-shaped tower with a ground circumference of 56 meters, 14.5 meters high, crowned with an octagonal. On the southwest side of the tower is a door that leads to an even bigger and higher bridge over the moat.