The Great Wall of China was started as early as the 7th century BC; these, later joined together and made bigger and stronger fortification. Especially famous is the wall built 220-206 BC by Qin Shi Huang, the first Emperor of China. Little of that wall remains. The Great Wall has been rebuilt, maintained, and enhanced; the majority of the existing wall is from the Ming Dynasty (1368-1644). It was built along an east-to-west line across the historical northern borders from the Bohai Sea to the Gobi desert to protect the Chinese states and empires against the raids and invasions of the various nomadic groups of the Eurasian Steppe, particularly the Mongals and the Huns.
Read more on the (Wiki link).

We visited the wall at Badaling

Autumnal colours of the trees