The Great Wall of China looks like a giant dragon lying across the mountains and desert. It is the worlds largest man-made structure. The Chin dynasty built a long defensive wall to repel invaders from the north, during the 3rd century BC.
Successive Emperors, from that time on up to the 17th Century, continued to build long walls. If they were all combined the total length would be around 50,000 kilometres. However, the walls disintegrated over time. Many of the ones remaining today originate from the Ming dynasty.
This section is known as the Lao Long Tou, the Old Dragons Head. The Dragon of the Ming Dynasty starts here and runs across the country for 3,000 kilometres.
This is the first and the most eastern checkpoint, known as Shan-Hai-Guan. Several gates like this are placed in strategic positions. Its solidly built, made of specially-hardened bricks. Thats why the walls of the Ming dynasty are still standing.
The defensive wall stretched over the steepest mountains serving as the national border. The authorities wanted it to unify those states inside the wall and separate those outside. 1,200 kilometres inland in the East, the wall meets the Yellow River, the mother of ancient Chinese civilization.
The Huang Tu Plateau an area of arid land extending 1,000 kilometres east to west is on the other side of the river. The wall stretches across the plateau and is partially buried in sand.
The wall here is made entirely of earth and has been badly eroded.
Locals are restoring it using a traditional earth-ramming technique. First they make a wooden frame and place earth inside. The earth is then hammered until it is compact, then new soil is placed on top and the procedure repeated.
The last checkpoint is in Gansu province, 3,000 kilometres from the east coast. Its called Jia Yu Guan and is the largest existing gate. It was an important military base for the western part of the wall. There were about 400 soldiers garrisoned here. More walls dating back from the Han period were found from this point.
The long wall was built some 2,000 years ago to protect the Silk Road. It extended 3,500 kilometres (from the eastern sea coast). The tail of the giant dragon is gradually being buried under the desert sands.