Jiayuguan.

It is known as "the most powerful pass in the world". It is located in the middle of the narrowest valley 5 kilometers west of Jiayuguan City, Gansu Province. The city walls on both sides of the city pass cross the Gobi Desert and are connected to the Black Mountain Cantilever Great Wall to the north and the No. 1 Pier in the World to the south. It is the westernmost pass of the Ming Great Wall. Jiayuguan is a transportation fortress on the ancient "Silk Road". Jiayuguan was first built in the fifth year of Hongwu in the Ming Dynasty (1372). After more than 160 years of construction, it was finally completed in the eighth year of Hongzhi in the Ming Dynasty (1528). The last large-scale reconstruction project of Jiayuguan was in 2017, which lasted five years and involved an investment of approximately 305 million yuan, aiming to restore its historical majesty.