Being the natural cave with the length of more than 500m and other grandiose beauty, Nhi Thanh Cave is closely related to the well-known person named Ngo Thi Si who discovered this cave and restored it to be the attractive destination in May 1779. Nhi Thanh Cave is quite large with lots of corners, stalactites in many different shapes. From the main gate looking up, people could see the Tam Giac pagoda (triangle pagoda) which honors Confucius, Laozi, and Buddha. There is a statue, which is carved into the limestone portrait Ngo Thi Sy. On the cliff of the cave, there were also many poems written by him.
Being the pagoda of three religions, there are many statues of Gods under different figures: Nhi Thanh cave is related to Ngo Thi Sy when he was assigned to be the head of Lang Son province from 1777-1780. In this short period, he changed the appearance of Lang Son of all the aspects especially the cultural one: he discovered eight beautiful spots of Lang Son, which includes Nhi Thanh cave.
In May 1779, he hired the workers to rebuild this area of cave. The left cave is higher with tougher land, so it is suitable for pagoda. Nhi Thanh cave is under the pagoda of three religions.
There are still many steles inside this cave recording the doctors and well-known people crossing this cave and left. This is the precious resource for literature history, Lang Son history and art history.