Introduction to the rain and fog arc: It usually appears in the early morning after the summer and autumn rains in Riyueya. At this time, clouds were flying across the fog around the Riyue Cliff, and suddenly a few rays of arc light passed through the gaps in the clouds and fog, and passed from the edge of the cliff. They were so dazzling that the stone patterns on the hazy Sun and Moon Rock were clearly distinguishable. There was no thunder after the arc, and it is called the second mystery of Huashan.