The Great Wall of China is a monumental construction that includes a complex system of walls, horse tracks, watch towers, shelters, passes, and border fortresses. It begins in Shanhaiguan in Hebei province in the east and ends at Jiayuguan in Gansu province in the west.
In contrast to the still-persistent popular image, the Great Wall of China isn’t one continuous fortification. Rather, it was built over the course of almost 2,000 years by many different dynasties. Therefore, it is difficult to determine its precise length.
Beginning in 2007, teams of Chinese archaeologists spread out to cover 15 provinces, measuring every trace of the Great Wall they could find (over 2,000 people were involved in the project). By 2012, they found the wall to be 21,196.18 km long. In comparison, the Earth’s circumference is 40,075 km at the equator.
This measurement included not only the parts still standing, but all which were ever built. It is interesting that the Great Wall is probably even longer, since some parts of it lie in the Gobi desert, outside the political borders of modern China (i.e. in modern Mongolia).
It is also possible that some sections of the wall remain undiscovered – sometimes it is difficult to distinguish between the remains of a section of the Great Wall and what is simply an old defensive wall unrelated to that structure.
The survey estimated that only 8.2% of the wall that was built under the Ming dynasty remains standing, and most of it is in poor condition. Therefore, the survey also had the goal to assist in the preservation of the structure.