While serving as an administrator for Hangzhou , the poet Su Shi ( 1037 – 1101 ) had a large pedestrian causeway built across the West Lake , which still bear his name : Sudi ( 蘇堤 ) . In 1221 , the Taoist traveler Qiu Changchun visited Genghis Khan in Samarkand , describing various Chinese bridges encountered on the way there through the Tian Shan Mountains , east of Yining . The historian Joseph Needham quote him as saying :