Tanxian Ridge is a historically important pass, which had been a military strategic position for its strategic importance and easy defence, and is known to be "Badaling Ridge in the South" . On the ridge, a stone fortress was built with 72.4 meters long from north to south, 41.3 meters long from east to west and 5.7 meters high. This fortress has been named "the smallest stone fortress in China" by the headquarter of World Guinness Records in Shanghai".The name of the Ridge was said to be related to Tan Qiao, a daoist in South Tang dynasty. According to traditional account, there was a Tanxian Temple on the ridge where Tan Qiao made pills of immortality. At present time, there are remains of fairy footsteps, stone bathtub and wells of alchemy.