The Grand Canal is a 1,000 mile (1,610km) route that goes from Hangzhou to Beijing and forms the longest man-made waterway in the world. While parts of the waterway date back 2,500 years ago, the main effort was made during the Sui Dynasty in the 7th century. Megalomaniac emperor Yangdi had great vision and great projects, including rebuilding the capital Luoyang and the Great Wall. His purpose behind the canal was to create a link between the fertile Yangtze region and Luoyang to transport not only grains, but also soldiers in times of unrest.
As with the Great Wall, construction on the Grand Canal was by forced labor. Once completed, subsequent dynasties would use the canal to its fullest, even placing the capital of the Song dynasty in Hangzhou along its banks. The Yuan dynasty extended the canal to Beijing to transport food and gave us the canal's present form.
Today, the canal is silted up from Beijing to Tianjin, but remains operative south of the Yangtze River. The canal was built to be functional rather than aesthetic but can be an interesting historical alternative to the train when traveling between Suzhou and Hangzhou.