[["It is believed the original Great Wall was built over a period of approximately 20 years.", 576.0], ["Over 20 years", 396.0], ["The Great Wall was built over many years. It is believed the original Great Wall was built over a period of approximately 20 years. The Great Wall which is mainly in evidence today was actually built during the Ming dynasty, over a period of around 200 years.", 73.0], ["Many centuries", 7.0]]
how long did it take to build the wall of china
history,china