Lang Son is a booming city set next to tranquil Phai Loan Lake and surrounded by green karst peaks. Most travellers pull through town on their way to or from China (the border is 18km north, just outside Dong Dang). If you need to spend the night, there are a few attractions to keep you entertained, such as the caves located 1.5km from the city centre.
The area is populated largely by Tho, Nung, Man and Dzao tribal people, though their influence is not evident in the city. Lang Son was partially destroyed in February 1979 by Chinese forces, and the ruins of the town and the devastated frontier village of Dong Dang were shown to foreign journalists as evidence of Chinese aggression. Although the border is still heavily fortified, both towns have been rebuilt and Sino–Vietnamese trade is in full swing again.