The Great Wall is about 2,400 km (about 1,500 mi) long, according to conservative estimates. Other estimates cite a length of 6,400 km (4,000 mi), or even longer.

The world will have to wait till 2008 to know the accurate length of China's Great Wall, one of the seven man-made wonders of the world.
A massive geographical survey of the Great Wall has been launched by China's State Administration of Cultural Heritage and State Bureau of Surveying and Mapping.

The survey will be completed by 2007 and the basic statistics of the Great Wall, including its length and layout, will be released in 2008, officials said in Beijing on Thursday.

Local governments have been gathering statistics on the Great Wall since the 1980's. "Due to limited knowledge and technology at the time, most parts of the Great Wall remain unknown to us," director of the SACH, Shan Qixiang said.

"It's necessary for the government to organise a scientific survey so we have a comprehensive and accurate understanding of the Great Wall," Shan said.

The wall is generally considered to start at the Jiayuguan Pass in Gansu Province and stretch 6,000 km to the Shanhai ...more

The Great Wall is the world's longest human-made structure, stretching over approximately 6,400 km (4,000 miles) from Shanhaiguan in the east to Lop Nur in the west, along an arc that roughly delineates the southern edge of Inner Mongolia. It is also the largest human-made structure ever built in terms of surface area and mass.

it is 2400k.m. built with mud & stone.

It was over 5,000 km (=10,000 Li) long. Its thickness ranged from about 4.5 to 9 meters (15 to 30 feet) and was up to 7.5 meters (25 feet) tall.

During the Ming Dynasty (1368-1644), the Great Wall was enlarged to 6,400 kilometers (4,000 miles) and renovated over a 200 year period, with watch-towers and cannons added.

I think 3500 KMs.