Before I came to Dunhuang to do my homework, I really didn't see Hecang City. It was the driver of the chartered car who introduced it to us. After that, I felt very spectacular. At least, it attracted me more than Yumenguan. Hecang City is built on a terrace about 3 meters above the lake beach, and there is a large Gobi hug several feet above the castle in the north and south, which makes it extremely concealed. It is very difficult to find this warehouse without approaching it. Thus, the ancients took a lot of pains to choose this place to build military warehouses. It's really good to come here and learn about this history by the way. Immediately I thought of a sentence "Reading ten thousand books is better than traveling a thousand miles".