The Great Wall of china is also called as "Long city/fortress" and "The long wall of 10,000 Li",The Great Wall of China is a series of stone and earthen fortifications in the northern China,built to originally protect the norther borders of the Chinese Empire against intrusions by Xiongnu from the north,the construction of the wall started in the 5th century BC,the rebuilding and maintance work went on till 16th century.
The Great Wall of China stretches from Shanhaiguan in the east to Lop Nur in the west,
Length of the wall
The most comprehensive archaeological survey,using advanced technologies has recently concluded that the entire Great Wall,with all of its branches,stretches for 8,851.8 Kms(5,500.3 miles).This is made up of 6,259.6 Kms(3,889.5 miles) of actual wall,359.7 Kms(223.5 miles) of trenches and 2,32.5 Kms(1,387.2 miles) of natural defensive barriers such as hills and rivers.
Condition
While some portions in the north of Beijing and near tourist centers have been preserved and even extensively renovated,in many locations the wall is in despair.More than 60kms(37 miles) of wall in Gansu province may disappear in the next 20 years due to erosion from sandstorms.And in some places the height of the wall is reduced from original 5mts height to 2mts and less.
Visibility from Moon
Popular beliefs from 1930s Ripley's Believe or Not's cartoons,which claimed that the Great Wall of china could be visible from moon but no astronaut has agreed upon it.And surveys have cleared saying that its not possible to see the wall from moon by naked eye.In fact its like seeing human hair from 2 mile distance,and confirmed that human eyes to see the wall from moon requires spatial resolution 17,000 times better than normal vision.
