Riyue Shan — Sun and Moon Mountain — is the low pass on the road from Xining to Qinghai Lake, long regarded as the symbolic threshold between the Chinese agricultural world and the Tibetan pastoral plateau. The pass sits at 3,520 metres and is visible from the road; two small pavilions mark the spot, one traditionally called Sun (Ri) and one Moon (Yue), though the current structures are 20th-century reconstructions.
The cultural significance is considerable. This is where the Silk Road to Central Asia and the Tang-Tibet road diverged, and where countless travellers throughout history registered the shift from terraced farmland to open grassland. Today it is a quick roadside stop on most tours to Qinghai Lake, but worth a short walk for the view east over the valley and west across the beginning of the high plateau.