T’ungkwan, China (Google Maps ⧉, OpenStreetMap ⧉)

"The most notable fortress of the Kin sovereigns was that of T’ungkwan, on the right bank of the river, 25 miles below P’u-chau fu, and closing the passage between the river and the mountains, just where the boundaries of Ho-nan, Shan-si, and Shen-si meet."