CHINA'S GREAT WALL LONGER THAN THOUGHT

The Great Wall of China is even greater than previously thought, according to the first detailed survey to establish the length of the ancient barricade. The wall, the world's largest man-made structure, was built to protect the northern border of the Chinese Empire. Known to the Chinese as the "long Wall of 10,000 Li", the Great Wall is in fact a series of walls and earthen works begun in the 5th Century BC and first linked up under Qin Shi Huang in about 220BC.

A two-year government mapping study found that the wall spans 8,850km (5,500 miles) - until now, the length was commonly put at about 5,000km. Previous estimates of its length were mainly based on historical records. Infra-red and GPS technologies helped locate some areas concealed over time by sandstorms, state media said.

The project found that there were wall sections of 6,259km, 359km of trenches, and 2,232km of natural defensive barriers such as hills and rivers.

Experts said the newly-discovered sections of the wall were built during the Ming Dynasty (1368-1644), and stretch from Hu Mountain in northern Liaoning province to Jiayu Pass in western Gansu province.

The project will continue for another 18 months in order to map sections of the wall built during the Qin (221-206BC) and Han (206BC-9AD) Dynasties, the report said.

It was listed as a Unesco world heritage site in 1987.