Riyue Mountain (Sun-and-Moon Mountain), part of the Qilian Mountain Range, is located in the west of Huangyuan County, Qinghai Province. In the past, it was a vital communications center between central China and the southwest frontiers as well as the west regions. Later on, Princess Wencheng of the Tang Dynasty (618-907) passed Riyue Mountain when she was going to marry Songtsen Gampo, king of the Tubo tribe. To commemorate the princess, the mountain was renamed the Sun-and-Moon Mountain, and the Princess Wencheng Temple was built at the foot of the mountain.[China.org.cn/Photo by Han Jiajun]