Due to the large number of people walking on the Zhongshan Iron Bridge, it is inconvenient to pass. In fact, it was discovered when riding a shared bicycle to the Baita Mountain Park on the Yuantong Yellow River Bridge next to it. The ruins are hidden behind a bus station and environmental public toilets. There is a small hill with a monument and a pavilion on the slope. There is almost no trace of it. At the beginning, I didn't know what a kind of city system was called "baocheng", but after I came back, I found out that it was the city built by Yuan General Wang Baobao to resist the Ming army's attack on Lanzhou. Perhaps these histories have long been forgotten or neglected, but they piece together such a splendid Chinese culture little by little.