br Iconic Longest Wall In The World|Awe-inspiring Feat Of Defensive Architecture|Secrets Of World Landmark br br #levelup4u|| #informativebr br The Great Wall of China became a UNESCO World Heritage Site in December 1987. The wall is the longest man made structure in the world, with a total length of about 13170.7 mi or 21196.18 km. Made over the course of hundreds of years, the wall was built by over 6 different Chinese dynasties, and is over 2,300 years old.