As the gateway from Shanxi to Hebei province, Niangziguan (Women’s Pass) is 45 kilometers away from Pingding County town center, located to the northeast of Yangquan. Originally called Weizeguan Pass, during the Sui Dynasty, Niangziguan is well-known as the ninth pass of the Great Wall, due to its strategic position. An attractive feature of the location is a castle that stands high up on the cliff of undulating ridges, facing the Taohe River . In the Tang Dynasty, Princess Pingyang, Emperor Li Shimin's sister, led an army of women stationed there, thus inspiring a name change to Niangziguan (Women’s Pass) in memory of those women soldiers. Inside the castle, there are south and east facing gates with 650 meters long walls. The old buildings, temples and houses are well preserved in their original state, enabling visitors to experience history, first hand .