I forgot about the pits. Those were useful. Well, one idea is that they could build the moat on the inside of Alexandria. Then remove the wall and put it back up on the other side of the moat. The wall really needs to be replaced. It's too easy to be climb and the supports are on the wrong side. This makes it not as stable and easier to climb as well.
They have the equipment and the man power to do this. I think about this stuff more than I should throughout the day