This is the largest engineering and building project ever carried out by humans. The Great Wall of China runs from east to west, from Shan-hai Pass near Bo Hai, a gulf of the Yellow Sea, to Chia-yu Pass in Gansu province.
The wall's length has been quoted as anywhere between 2,000 to 8,000 kilometres, but a comprehensive definitive survey has not been carried out. Nevertheless, by any reckoning, the wall is an awesome achievement.
China has had walled cities from the earliest times, but it was emperor Shih Huang Ti who ordered existing sections of wall to be connected to form one long wall, when he united different parts of the country into one China in around 214 BC.
Since that time it has been extended and rebuilt countless time. Only parts of the wall remain, but it has been reported that if the surviving sections were placed end to end, they could stretch from Los Angeles to New York.
The wall built of dirt, stone and brick was used as a defence barrier against invading nomads and wandering tribes.
Despite the wall�s cultural significance, roadways have been cut through it and sections have deteriorated through neglect, but parts still attract thousands of visitors who marvel at this amazing human achievement.