【英文写作】介绍长城的情况（开头和结尾已经给出）

Dear Teddy,
Hearing the news that you would come to China to visit the Great Wall,I was overjoyed.Considering your deep interest in ancient cultural heritage,especially that in the Great Wall,I'd like here to give a brief introduction.
　Loacted in the northern part of China,the Great Wall,with its total length of 6,700 kilometers,was registered in the World Heritage List in 1987.It has been built since Qin Dynasty,the original purpose of which is to defend the country against outward attack /invasion.The Great Wall is the miracle created by ancient Chinese working people,and is one of the greatest projects in human history as well.
Wish you all the best.Hope to see you soon!
Yours,
Li Hua