It used to contain a fortress of wood protecting the entrance into the valley and a small "village" that could easily house an army, as it does in the Emperor of Nihon-Ja. There is an exit and a watchpoint which looks out over the mountains and passage leading into the valley, both aren't easily accessible or found but in the book they are used to mount an attack against Arisaka's army by Will and his friends.The sides of the fort are natural massive cliffs that are impassable by any army. There was also a hidden path which led out of the fortress, for if the defenders had to retreat.