The spectacle is at the top of Wang Hat Mountain at the western end of the Great Wall. At an altitude of more than 700 meters, there is a long narrow valley behind the hillside, called "Xiaoqing Snake Valley". Every day the weather changes, a cloud of smoke rises from the green snake valley. First, it spreads and expands along the hillside, then gradually covers the mountainside and covers the top. Clouds and mists, like clouds and not clouds, like fog and not fog, the sky is low and cloudy, the Great Wall is also like a green dragon soaring clouds and driving fog, so it is called "cloud sea smoke wave".