HOW LONG DID IT TAKE TO BUILD THE GREAT WALL OF CHINA?
The Great Wall isn’t a single wall at all, but a series of bulwarks and fortifications. The first went up some four centuries before Qin Shi Huang, who became China’s first emperor in 221 BC, ordered a decadelong project to unite and expand these defences into a single barrier.
Construction to create the current 13,000 miles of wall continued, on and off, for more than two millennia. Much of what remains was built during the Ming Dynasty. While intended to keep out foreign invaders, Genghis Khan demonstrated how even a wall as great as this had a flaw. He marched his Mongol horde around one of the sides.