Lang Son is also a province in northeastern Vietnam. Lang Son has two international border gates: Dong Dang railway station and Cao Huu Nghi border gate; There is a national border gate: Chi Ma (Loc Binh District) and 10 border crossings with China. The mountainous area occupies over 80% of the province. The topography in Lang Son is low mountains and hills with an average elevation of 252 m above sea level. The lowest point is 20 m in the south of Huu Lung district and the highest is Mt Mau Son 1541 m. Mau Son is 31km east of Lang Son city, surrounded by many small mountains with occasional snowfall in winter. The climate of Lang Son clearly reflects the humid subtropical climate of the North. Vietnam. The distinct seasonal climate, in different seasons, is unevenly distributed due to the complexity of the mountainous terrain and the rapid denaturation of cold air in the interior of the tropics. significant differences in thermal regime between regions.