Introduction to Tiansheng Bridge: There is a natural Tiansheng Bridge under the majestic cliff, spanning the Nanxi River. The terrain is steep and the water is turbulent. It has been a tunnel leading from Mongolia to Vietnam along the river in ancient times. An important defensive location on the southern border. There is a stone carving on the cliff east of the bridge, which is "Key to the Rock Frontier" inscribed by Liao Yingchang, a monk who had already drawn pictures in the 25th year of the reign of Emperor Guangxu of the Qing Dynasty (1899). Each character is 1 meter square, written horizontally in regular script, inscribed in clear, and clear. The writing is vigorous.