洮河
The frontier walls built by different dynasties have multiple courses. Collectively, they stretch from Liaodong in the east to Lop Lake in the west, from the present-day SinoRussian border in the north to Tao River (Taohe) in the south; along an arc that roughly delineates the edge of the Mongolian steppe; spanning over in total. Today, the defensive system of the Great Wall is generally recognized as one of the most impressive architectural feats in history.