Introduction to Tongtian Gorge: Formerly known as Yixiantian, the silicate stone walls on both sides of the place are steep and straight up to the blue sky, as if a narrow gap has been carved out by a miraculous craftsmanship. It is said that Liu Bocheng, commander of the Eighth Route Army, passed here when he led his troops over Motian Ridge and once said: "From here you can reach the sky ("Tian" refers to Motian Ridge)." Therefore, the common people of this generation later changed the name from "One Line of Sky" to "Tongtian Gorge".