Grand Canal, Chinese Da Yunhe [large transit river], longest in the world, extending c.1,000 mi (1,600 km) from Beijing to Hangzhou, E China, and forming an important north-south waterway on the North China Plain. The canal was started in the 6th cent. BC and was constructed over a 2,000-year period. Its largest sections were completed in AD 610 under Emperor Yang Ti of the Sui dynasty and were built by dredging and linking existing canals. Tree-shaded roads, postal stations, and imperial pavilions were built along the canal. Between the 10th and the early 13th cent. the waterway fell into disrepair. Kublai Khan reconstructed the canal in the 13th cent. and extended it to Beijing. Improvements were made during the Ming dynasty (1368–1644). Today the canal follows the Bai River south from Beijing to Tianjin; the 250-mi (412-km) section S of Tianjin ties into the Wei River. Leaving the Wei, the canal runs past Jining and through the elongated lakes of Shandong prov., then past Xuzhou and the lakes of Jiangsu prov. to cross the Chang at Zhenjiang. It runs generally south through the Chang delta, past Wuxi and on to Hangzhou, the southern terminus. The canal is 100 to 200 ft (30–61 m) wide and from 2 to 15 ft (.6–4.6 m) deep. Railroads, roads, and widespread silting have reduced its economic importance, but the canal remains navigable between Jining and Hangzhou and is a busy waterway S of the Chang.