The contents of 200 clay pots found near Rizhao (Shandong) in 1995 and dated to 2,600 BC indicate that grapes were grown in China as early as 4,600 years ago. Residues of grape wine were found in them. The explorer Zhang Qian (195-114 BC) returned from his travels in the West in 138 BC during the Han Dynasty and brought back 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) reports of vine plantations and excellent wine in the northeastern Taiyuan region. In the 14th century, however, many vineyards were cleared by imperial order in favour of grain cultivation.