Europe and featured the first known endless power-transmitting chain drive.
Kaifeng reached its peak importance in the 11th century when it was a commercial and industrial center at the intersection of four major canals. During this time, the city was surrounded by three rings of city walls and probably had a population of between 600,000 and 700,000.
It is believed that Kaifeng was the largest city in the world from 1013 to 1127.
This period ended in 1127 when the city fell to Jurchen invaders (see Jingkang Incident) and subsequently came under the rule of the Jin Dynasty. While it remained an important administrative center, only the city area inside the inner city wall of the early Song Dynasty remained settled and the two outer rings were abandoned.
One major problem associated with Kaifeng as the imperial capital of the Song Dynasty was its location. While it was conveniently situated along the Grand Canal for logistic supply, Kaifeng was militarily vulnerable due to its position on the flood plains of the Yellow River.
Kaifeng served as the Jurchen "southern capital" from 1157 (other sources say 1161) and was reconstructed during this time. The Jurchen kept their main capital further north until 1214 when they were forced to move the imperial court southwards to Kaifeng in order to flee from the Mongol onslaught. In 1234 they succumbed to the combined Mongol and Song Dynasty forces. Mongols took control, and in 1279 they conquered all of China.
At the beginning of the Ming Dynasty in 1368, Kaifeng was made the capital of Henan province.
In 1642, Kaifeng was flooded by the Ming army with water from the Yellow River to prevent the peasant rebel Li Zicheng from taking over. After this disaster the city was abandoned again.
Under the celebrated Qing emperor Kangxi (1662), Kaifeng was rebuilt. However, further flooding occurred in 1841 followed by another reconstruction in 1843, which produced the
