The ATK is the abbreviation for “An Toan Khu”, meaning “safe zone”, and consists of a network of underground tunnels with strong defense works able to withstand bombs and bullets. This zone was built during the war against the French and consists of a network of underground tunnels with strong defense works able to withstand bombs and bullets. These relics will be restored to become an attractive tourist site. This site is located in Bang Lung Townlet, Cho Don District, Bac Kan Province.