Located 30 kilometers northeast of Busan County, more than 1600 meters above sea level. There are two mountains, namely, the East and West Twin Peaks, the gap in the middle, shaped like arrows, because of its name. Again, Tang Taizong Li Shimin in the open road to the 90% palace, there is a very narrow, hard stone wall, the people are difficult to dig, so let the general captain Qi Jingde with arrows, after several arrows, a pile of earth and stone open, so called "arrow open", after word of mouth, read "arrow open".