the Great wall of china is one of great wonders of the world. it runs for 6700 kilometers across deserts, grasslands,mountains. the construction of the wall began in the 3rd century A.D. and was rebuilt in the 15th and 16th centuries. it was originally built in separate pieces to protect China from invaders. in 214 B.c.,Emperor qin shi Huang unified the country, and he joined the walls together into one huge wall. it took ten years to finish. the great wall is a monument to the building skills and to the wisdom and patience of the Chinese people.