Great Wall of China longer than believed as 180 missing miles found - 3 June 2011

The Great Wall of China is even greater than once thought, after a two-year government mapping study uncovered new sections totalling about 180 miles, according to a report posted on the website of the country's national mapping agency.

Using infrared range finders and GPS devices, experts discovered portions of the wall concealed by hills, trenches and rivers that stretch from Hu Shan mountain in northern Liaoning province to Jiayu Pass in western Gansu province, the official China Daily reported on Monday.

The newly mapped parts of the wall were built during the Ming dynasty (1368-1644) to protect China against northern invaders and were submerged over time by sandstorms that moved across the arid region, the study said.

The additional parts mean the Great Wall – construction of which began more than 2,000 years ago to prevent incursions into China by the Mongols and others – spans about 3,900 miles through the northern part of the country.

The latest mapping project, a joint venture by the State Administration of Cultural Heritage and State Bureau of Surveying and Mapping, will continue for another year in order to map sections of the wall built during the Qin and Han dynasties (221 BC-9 AD), the China Daily reported.

Recent studies by Chinese archaeologists have shown that sandstorms are reducing sections of the wall in Gansu to "mounds of dirt" and that they may disappear entirely in 20 years. These studies mainly blame the erosion on destructive farming methods used in the 1950s that turned large areas of northern China into desert. In addition, portions of the wall in Gansu were made of packed earth, which is less resilient than the brick and stone used elsewhere in much of the wall's construction.

China in recent years has begun restoring parts of the wall as well as trying to curb commercial development on or next to the ancient structure.

The wall's modern sections around the Chinese capital date from the Ming dynasty, including those restored since the Chinese Communist party took power in 1949, and several areas – including the most popular, Badaling, just north of Beijing – draw hundreds of thousands of visitors each year.

Tourist encroachment also has been a problem in recent years, with state media saying that near Badaling almost every brick on a popular section of the wall has been carved with people's names or other graffiti.