A new study commissioned by the State Administration of Cultural Heritage and the State Bureau of Surveying and Mapping has found that the Great Wall of China is longer than was previously believed. History text books cited the length of the Great Wall at 6,400 km (4,000 miles). Now, however, that estimate will be changed to 8,850 km (5,488 miles), 6,260 km (3889 miles) of which are wall sections, 360 km (223 miles) -- trenches, and 2,233 km (1387 miles) – natural barriers, such as hills and rivers.