Chinese usually saying goes like that,"you are not a real hero until you have climbed the Great Wall".The Great Wall,one of the greatest wonders of the world,was enlisted in the World Heritage in 1987.Just like a gigantic dragon,it winds up and down across deserts,grasslands,mountains and plateaus stretching approximately 6,700 kilometers from east to west of China.With a history of more than 2000 years,some sections are now in ruins or even entirely disappeared.However,it is still one of the most appealing attractions all around the world owing to its architectural grandeur and historical significance.The wall was originally built in the Spring/Autumn Period,and Warring States Period as a defensive fortification.It went through constant extensions and repairs in later dynasties.In fact,it began as independent walls for different states when it was first built,and did not become the "Great" wall until the Qin Dynasty.The First Emperor succeeded in his effort to have the walls joined together to fend off the invasions from the Huns in the north after the unification of China.Since then,the wall has served as a monument of the Chinese nation throughout history.However,the wall we see today,starting from Shanhaiguan Pass in the east to Jiayuguan Pass in the west,was mostly built during the Ming Dynasty.The wall is complemented by defensive fighting stations,to which wall defenders may retreat if overwhelmed.Each tower has unique and restricted stairways and entries to confuse attackers.Barracks and administrative centers are located at larger intervals.In addition to the usual military weapons of the period,specialized wall defense weapons were used.