Born with the name of Chi (Red) Ridge, the Riyue Mountain had been an important thoroughfare to western China for many years and a crucial link between Han and Zang (Tibetan) people. There is a legend concerning the mountain: In the Tang Dynasty (618-907), the emperor gave in marriage his daughter, Princess Wencheng, to the leader of Tibet, Songtsen Gampo to improve the relationship between the two nations. When the princess reached this mountain and took a break, she felt a surge of homesickness. She took out the precious Riyue Mirror given to her by her father because she was told that it would show her hometown while yearning for her home. But she resolutely threw down the mirror so as not to miss her country any more, and continued her journey to the west. The mirror was broken in two pieces shaped like the moon and sun. From then, the mountain got its name, Riyue Mountain.
The Daotang (backflowing) River springs from the west of the Riyue Mountain flowing west to the Qinghai Lake (the largest inland salt lake in China). Again there is a well-known legend concerning the Princess Wencheng. When she passed by the mountain, her tears of homesickness dropped and became the Daotang (Backflowing) River. Its flow westward symbolizes the princess's resolution to never return. In fact, it is the only river flowing from the east to the west in China.
The Ri (Sun) Pavilion and the Yue (Moon) Pavilion were built on each side of the mountain pass in memory of Princess Wencheng. Vivid murals are painted to re-create the scene when the princess enters Tibet and her life there. In the twin pavilions, the Yue Pavilion particularly depicts the great pomp of the cultural communication Princess Wencheng brought to Tibet, including crop seeds, technology, medicine, and Buddhism. It was she who brought civilization to Tibet. The period from June to September is the best time to travel there with verdant grasses, wild flowers and tents on the slopes of the mountain providing the crowning touch to its plateau landscape.