Technology has shown the Great Wall of China is more than 2,000 miles longer than first thought.
The Chinese government carried out a two-year mapping project using GPS and infra-red technology.
The team found the wall is 5,488 miles, compared to the former estimate of 3,106 miles.
The undiscovered parts of the wall were found in the mountains and deserts of northern China. About 70% of it is actual wall, while the rest is a mixture of trenches and natural barriers such as hills and rivers, the Daily Telegraph reported.
The technology was used to physically map the structure, parts of which were first built 2,000 years ago.