Na Lu citadel was built from earth by Cao Bien in Tang dynasty, the 7th Ham Phong year (864) of the 3rd Chinese domination. In 1039, the 6th Thong Thuy year during the Post-Ly dynasty of King Ly Thai Tong, the citadel was capital of the self- overned country Truong Sinh with Nung Ton Phuc as the leader. In 1527, Mac Dang Dung dethroned Le dynasty and set up Mac dynasty. Le – Mac divided into South and North dynasties and were in conflict for a half of century. In 1592, when Mac dynasty was defeated in Thang Long, they retreated to Cao Bang and chose Na Lu for settlement and established Mac dynasty. This dynasty last for three generations: Mac Kinh Cung (1594-1625); Mac Kinh Khoan (1625-1638); and Mac Kinh Vu (1638-1677). Besides building a citadel, they also organized examinations, royal rituals and established music teams.
The citadel was quadrilateral, including four roads and four gates respectively in the northeast, northwest, southwest and southeast. It is said that the southeast gate was built with beautifully-decorated vaulted bricks; the door was made of solid Nghien tree root; and the base was a large flat stone. Today, the vestiges of the gate base and its stone foundation remain visible. Inside the citadel, there are four mounds corresponding to the four mascots: Long, Ly, Quy, Phuong (Dragon, Unicon, Turtle and Phoenix).
In August 1677, when Mac Kinh Vu was defeated by Le Huy Tong (Le dynasty), Mac dynasty lost ground and retreated from Na Lu citadel. In 1682, Le Van Hai, the proconsul of Cao Bang, requested King Le to repair Na Lu citadel and change the palace into King Le Thai To temple.
During the resistance war against the French colonialism, Na Lu citadel was also a secret meeting place of Vietnam’s Communist Party.
Na Lu citadel and King Le temple were recognized as National Monuments under Decision No. 837/QĐ-BVHTTDL dated March 3rd, 2009 and Decision No. 1568/ QĐBT dated April 20th, 1995.