In 1290, Kublai Khan, one of grandsons of Genghis Khan, was building his glorious capital of Yuan Dynasty(1271-1368) in Chinese history, Dadu(Khanbaliq) - today's Beijing.
The city wall had been completed and white-colored gates had been already under construction. The city moat was taking form...One of his ministers, and a brilliant engineer in history, Guo Shoujing had located a great water source for Kublai's capital and had constructed a canal, which carried sufficient water into Dadu. The canal ended at Dadu's harbor, today's Houhai area. But to build a capital, it needed also a huge amount of timber, brick and coal, so was an abundant amount of food. Both building material and food were available mostly in Central and South China, but not in North China. What to do?
There was of course the famous Imperial Way: The Grand Canal was originally built in year 605 during Sui Dynasty (AD 581-618), running 2,500 km all the way from today's Hangzhou up to Tongxian, a mere 17 km east of Kublai's new capital. Kublai Khan re-dredged the old Sui Grand Canal and escavated a new section between the Yellow River and the Yangtze River, shortening the length to some 1,800 km. It was capable of transporting commodities and food. But it was still costly and inefficient to transport goods over land all the way from Tongxian to Beijing. A solution was badly needed.
Kublai again called upon his "super" engineer, Guo Shoujing, to construct "the missing link", the Tonghui Canal, later named by Kublai himself. The connection started from Houhai along the eastern end of the Imperial Palace in today's Beiheyan and Nanheyan. The water passed under the southern city wall and followed today's Zhengyi Road until turning east along today's Qianmen Street. It then flowed 17 km in the newly escavated Tonghui Canal all the way to Tongxian, where it joined up with Wenyu River, a major North-South local river, which turned into the Grand Canal south of Tonghui Canal. Because of the topography, Guo Shoujing also had to build some 24 lock gates to regulate water levels.
By 1293, Kublai Khan with the aid of Guo Shoujing, had indeed solved the task of securing an efficient and economic flow of commodities and grain into his new, thriving capital of Dadu. The capital could now be finished. The best craftsmen ensured that the Imperial Palace was fit for an emperor ruling the largest expanse of territory ever. The gates and city moat were completed. Large warehouses were located close to the gates inside the city gates. The area around the Imperial Palace was surrounded by the famous Hutongs. The northern areas inside the city wall were left as hunting grounds for the Khan's mongols.
In the subsequent Ming dynasty (1368-1644), the city was expanded and the south city wall was moved south so that the inner city canal became an underground river. The canal ended at southeast corner tower of the Ming and Qing dynasty up to today. Since the last years of Qing dynasty, Tonghui Canal is serving as the city channel for discharging flood instead of a transport line.