Onsong lies along the
Tumen River, which forms the border with
China. To the north of Onsong is
Jilin Province, China. Onsong also contains the northernmost point in
Korea, at 43°0'39″ N.
Liangshui (), in
Tumen prefecture, is the closest Chinese town across the river. The land of Onsong is mainly mountainous, although a part is flatland. It has a
continental climate, and is the region of Korea with the longest winter, except the
Kaema Plateau. The highest peak is Yŏndubong. ==Economy==