Introduction to Gongjiadong: Gongjiadong is located in the north of Xiaojing and was formed by the collapse of the roof of the underground river cave in Xiaojing. The cave is a rectangular skylight about 300 meters long, 200 meters wide, and about 150 meters deep. The skylight is surrounded by karst cone peaks. The rock walls on both sides are steep and smooth, like a knife cutting an axe.