The lack of fortifications in the walls due to the fact that in the pre-cataclysm city it was an inner wall, not really meant for an hard defense. However, it is practically insuperable by the tecnological standard of the "current" world. This is not that important for the city, after all, because an enemy should first put foot on the large island on which the city now is located, and that would be prevented by the total control of the sea Iramir enjoys.