The contents of 200 clay pots found in 1995 near Rizhao (Shandong), which were dated to 2,600 B.C., indicate that wine was cultivated in China as early as 4,600 years ago. Residues of grape wine were found in these. The explorer Zhang Qian (195-114 BC) returned from his travels in the West in 138 BC during the Han Dynasty, bringing with him knowledge of viticulture. The first written documents date back to the Tang Dynasty (618-907), when Emperor Li Shimin vulgo Taizong (599-649) noticed the special quality of the grapes from the Turpan Basin, which is why he had his domain extended to the northwestern region of Xinjiang. As early as the mid-7th century, vinifera varieties called Snake, Mare's Nipple and Dragon's Pearl were probably introduced from Russia. Marco Polo (1254-1324) reported vine plantations and excellent wine in the northeastern Taiyuan region. In the 14th century, however, many vineyards were cleared by imperial order in favor of grain crops.