Tam Thanh cave lies in the middle of a range of mountains in shape of herd of elephants on a green glass surface.
The cave entrance faces the east, is approximately 8m high, with a including 30 stone steps carved into the side of the mountain. The right wall of the cave has a carved a poem from Ngo Thi Si (1726 – 1780) when he worked as the chief of Lang Son Province. The poem praises the grandiose beauty of nature. Tam Thanh and Nhat Thanh, Nhi Thanh, Tien pagoda, Ky Lua, Ky Cung River, Vong Phu mountain, and the legend of To Thi create an attractive beauty for tourists when they visit the Lang region