Named after both the sun and the mon, Riyue mountain is a site of contrasts. It marks a division in geography and as such the two sides of the mountain are distinct and different. The east is rural highland scenery while the west is grassland. It is said that in the year 641 AD, Princess Wencheng stopped on this mountain while on route from Tang dynasty China to Tibet to marry the Tibetan King Sunzanganbu and that during her visit she left behind a valuable mirror. The Ri and Yue pavillions are built in her honour.