The Five Forts
From A Wiki of Ice and Fire
The Five Forts are many, many leagues to the east of the Bone Mountains. Forts are usually military constructions and buildings designed for defense.
The Five Forts appear to be five man-made forts that may guard and defend the south-western borders of the Land of the Shrykes and the cites of K'Dath and Bonetown. How long they have been in existence is not known.
They appear to be quite large and formidable. Whom the peoples of that part of the world need to defend themselves from is not known. They may be in good repair as they are not marked as ruins. They appear to be guarding the only entrance to that part of the world as there are natural borders, such as the Bleeding Sea, preventing entrance from other westerly directions.
Behind the Scenes
Wonders Made by Man
Thus far there are four confirmed man-made wonders. In total there are nine, meaning that five more are so far unidentified. It is quite possible that the Five Forts may be one of the unknown wonders, if Lomas Longstrider managed to reach that far east. It is said that he “traveled the world.”