Introduction to Cuona Lake: Cuona Lake is a plateau freshwater lake and the source lake of the Nu River. It covers an area of about 400 square kilometers and has an altitude of 4,650 meters. It is the highest freshwater lake in the world. If you take the train, you will pass by this quiet and beautiful sacred lake. If you have time, you can go to the observation deck here to overlook Zhuoge Peak in the distance and watch the fish and birds playing up close, which is a unique experience.