Lou-lan ［楼蘭］ (PY Loulan;  Rōran): An oasis city-state in Central Asia during the Han dynasty (202 b.c.e.–c.e. 220) of China. The remains of Lou-lan are in the present-day Sinkiang Uighur Autonomous Region of China. Lou-lan lay by the northwestern shore of the lake Lop Nor (Lop Lake) on the eastern rim of the Tarim Basin and prospered as a center of East–West trade along the Silk Road. Because Lou-lan occupied an important position, the Hsiung-nu (known in Europe as the Huns) and the Han Chinese often warred with each other over its possession; consequently, it fell at different times under the rule of the Hsiung-nu or the Han. In 77 b.c.e. the Han killed the ruler of the Lou-lan kingdom and renamed it Shan-shan. From the first century onward, Shan-shan gradually annexed the oasis city-states lying to its south and southwest and along the foot of the northern slope of the Kunlun Mountains. From the fifth century onward, however, the Shan-shan kingdom was invaded by various tribes and gradually declined, until ultimately it was buried under the desert sands. Through excavation and research conducted early in the twentieth century, it became clear that Lou-lan had at one time been a great center of Buddhism in Central Asia.