Here is the wonder of the world, "A Line of Sky", which is the crevice of the main peak rock mass. The rock walls on both sides stand upright as if it had been cut by an axe. Standing in the deepest part of the stone crevice, you can only see a ray of blue sky, which is named "A Line of Sky". The deepest part is 31 meters, the total length is 71 meters, the widest part is about two meters, the narrowest part is less than half a meter, and the slope at the bottom is 40-50 degrees, which can only allow one person to climb through. It was originally a natural moat that no one could pass through. In 1999, county government funded to pave 80-meter-long stone steps with more than 490 levels for tourists to climb. According to the textual research, A Line of Sky was formed about 3 billion years ago in the Middle Archaean era, because of the folds and faults in the strata, it was evaluated as a Class II geological relic by experts, and was also regarded as "absolutely a world-class natural landscape" by Xinsheng Zhang, the president of the 28th annual meeting of United Nations Educational, Scientific and Cultural Organization (UNESCO).