Tam Thanh Pagoda in a stone cave ( also known as Tam Thanh Grotto) is located in Tam Thanh Ward, Lang Son City, Lang Son District. According to a historical book called Dai Nam Nhat Thong Chi, Tam Thanh Pagoda was built in Le Dynasty, located in Vinh Trai Commune, Thoat Lang District.

Over the vicissitudes of the history, Tam Thanh Pagoda retains its inherent natural beauty, attracting visitors from near and far. In Tam Thanh Grotto, there is a white big Buddha Amitabha statue in the flexible soft art style of Le - Mac Dynasty. The statue is in the standing position in the shape of a Bodhi leaf. It has the height of 2.02m and the width of 0.65m well-carved into the cliffs. The statue is covered with a buddhist priest’s dress shading from shoulders to the heels.

Below the statue, there are Tam Bao Palace and Am Ti (Hell) Lake which is blue all year round with stalactites constructed by the nature and created majestic and vivid shapes.

Tam Thanh Grotto has the length of 50 meters and Thong Tien (Theosophy) Gate leading to the top of the mountain. Tam Thanh Steele says: "The grotto is created by the heaven and the earth. It is the sacred landscape of the talents and difficult to describe and paint."

The researchers said that previously Tam Thanh Pagoda was a place of worship of Taoism. Therefore, Tam Thanh meant Ngoc Thanh, Thuong Thanh and Thai Thanh which were three highest palaces and considered the three fairy scenes in which each scene was governed by a deity. Over the vicissitudes of history, today the marks of religion only remain its name and Tam Thanh Pagoda has become a relic of religious beliefs.

In addition to its scenic values, Tam Thanh Pagoda is  also known by the cultural values. Currently in the temple remains statue systems as well as plentiful epitaph of writers and poets over the historical periods. In particular, the stele number 4 (Ma Nhai) is the oldest carved in the second year of Le Vinh Tri Dynasty (1677) recording  the details of the construction and the renovation of the temple. The stele mentions a poem of Ngo Thi Si who was the director of Lang Son town in 1777. The poem praises the beauty of the charming Tam Thanh Grotto.

Tam Thanh is a complex including 3 caves ( Nhat Thanh, Nhi Thanh, and Thanh Tam) in Tam Thanh Pagoda. Tam Thanh Grotto is  located on a mountain in the shape of elephants prostrating on the green grass. Tam Thanh Grotto lies halfway up the mountain and can be reached by moving 30 stone steps carved into the mountainside. The right side of the grotto is carved a poem composed by Ngo Thi Si (1726 -1780) when he was the director of Lang Son.