Introduction to Changhai: Changhai is hidden deep in the mountainous valleys. It is the highest lake in Jiuzhaigou and the largest sea in Jiuzhaigou. Opposite Haizi, you can still see the snow-capped peaks, typical glacier landscapes such as cirques and "U" shaped valleys. The shore is lush with trees and water and grass. At a glance, you can see towering snow-capped peaks bathed in the blue sky and white clouds. The scenery is beautiful. Changhai is 3,060 meters above sea level, with the highest point at 4,457 meters, and an area of about 2 million square meters. About 8 kilometers long. The lake area is vast but has no surface outlet. During heavy rains in summer and autumn, the water does not overflow the embankments, and during long droughts in winter and spring, it does not dry up. Tibetans praise it as "a treasure gourd that cannot be filled or drained". In the middle of winter, the ice is 60 centimeters thick, and it is said that monsters appear here.