It is still not visible from space, but scientists have discovered that the Great Wall of China is about 1,000 miles longer than previously thought.
Most estimates have calculated that the barrier stretches for around 4,500 miles (7,300km) through the Chinese countryside, but modern mapping techniques have discovered that it is even greater.
A two-year study was carried out by the State Administration of Cultural Heritage and the State Bureau of Surveying and Mapping using GPS and infra-red devices.
The first modern measurement of the Great Wall found that there were wall sections of 3889 miles, 223 miles of trenches, and 1387 miles of natural defences such as hills and rivers making the entire barrier 5,488 miles (8,852 km).
Using mapping technologies such as infrared range finders and GPS devices, experts discovered portions of the wall, some concealed by hills or mounds of earth and sand, that stretch from Hu Mountain in northern Liaoning province to Jiayu Pass in western Gansu province.
The newly mapped parts of the wall were built during the Ming Dynasty (1368-1644) to protect against northern invaders and were submerged over time by sandstorms that moved across the arid region, the study said.