Lang Son is not the key tourist destination of Vietnam, but if there are some interesting things to do when staying there on your northeast loop tour.
1. 30km from Lang Son city, Mau Son offers stunning view and cool climate all year round. It is easy to get there by car, but it is a fun way to ride a motorbike to explore the area and take wonderfull photos.
2. Bac Son valley is about 160 km Hanoi and 70 km to Lang Son city. This scenic valley offers homestay experience, trekking tour and photography tour. Bac Son used to be unknown by international tourists, but they are coming now.
3. Shopping is a must in Lang Son if you are interested in cheap Chinese electronic products or devices. Dong Kinh, Ky Lua and Tam Thanh market are best places to go.
4. Mau temple is good place to stop. It is not about the temple, but about Mau belief in Vietnam. It is unique chance to see "Hau Dong" - A lady dressed colorfully, dancing as the god's spirit comes to her and diliver good luck, health and prosperity to others. More information, please look at https://www.vivutravel.com/vietnam-travel-guide/vietnamese-religion/mother-goddess-worship-in-vietnam
5. If you are in Lang Son, you definitely need to try the best Lang Son dish which is roasted duck.