Octagon City is located on the platform where the Yangqu River and Yangla River meet in the east of Ganga Beach, Xiahe County, Gansu Province. It is the key point of ancient Ganqing traffic, and it is also a military town where the central regime and the Tuguhun, Tubu, Xixia and Siamese dynasty have competed violently. The octagonal site is basically intact and listed as key cultural relics protection units in Gansu Province.