Yueyan, Daoxian County, Hunan, is a big rock mountain with empty top and belly. Based on the leftover rock structure and natural trend, it is made of natural and supernaturally crafted, naturally forming three caves in the east, middle and west. The moon cave gate is tall and towering, just like a city. Yankou is shaped like a moon, and from a distance, the sun shines like a bright moon hanging in the middle of a mountain. The three holes face each other, and the three points are in a straight line. Therefore, Moon Rock is also known as "Crossing Rock". Moon Rock is almost completely exposed in nature, showing an open state. This kind of open rock is rare in China and even in the world.