The man-made river that held China together — a thousand-mile spine of canals dug and maintained by vast numbers of conscripted laborers to carry the grain of the rich southern rice lands to the hungry capitals of the north, widely called the world’s longest canal, and among the oldest large artificial waterways still in use.
China's great rivers run the wrong way. The Yellow River and the Yangtze flow west to east, so they could move nothing between the rice fields of the south and the armies and courts of the north. So the Chinese dug their own river. The Grand Canal runs north to south for roughly a thousand miles, against the grain of the land, and for more than a thousand years it carried southern rice to northern capitals. It is one reason a country that size could hold together as one.