The streets of Mdina: In Mdina there are two kinds of streets. The curved streets were built during the time of the Arabs as a form of defense. Going up these narrow curved streets, one cannot gauge how long they are or, who is waiting at the other end. The streets built during the time of the Order of St John in the 16th century are built straight. The Arabs also built bastions, but the bastions built by the Arabs differ from the bastions built during the time of the Order of St John. The bastions built during the time of the Arabs are built vertically, because at the time of the Arab rule people used to climb up the walls and they would be thrown down to their death, whereas when the Order of St John came to Malta, gunpowder started being used and so the bastions were built slightly at an angle, so that the cannon ball would ricochet back on the person who fired it.