The Great Wall,snaking along the north of china with its starting point from the old dragon head of the shanhai pass at the seaside in the east,stretches westwards over a distance of 10,000 li. itcrosses the 3 provinces, 2 municipality and 2 autonomous regions of Hebei,Beijing,Tianjin,Shanxi,Inner Mongolia and Ningxia to end at Jiayu passin Gansu province in the4 west,its actual length totaling about 6,300kms,an equivalent of about 3,915miles.

Putting together the walls of suchlike built in various dynasties in ancient china the total length of the great wall can be up to more than 100,000 li about 31,075miles.except the great wall existing in the aforesaid provinces,umnicipality and autonomous regions,traces of walls as sunchlike can also be found in the provinces of Shandong,Henan,Hunan,and Hubei and some other places,However,in all these provinces and regions,the walls found in the Inner Mongolia autonomous region stretch the longest of them all,measuring approximately 30,000 li, an equivalent to 9,323 miles.

What were the fortresses,crenellated battlements and walled-in courtyard used for?

Fortress,used by the dfending troops to take shelter from the wind,rain and heat,fight and check the enemy's advance,and store arms and ammunition.

Crenellated battlements, the parts projecting upwards on both sides of the wall-top are called the crenels,which can be used for cover,defend and shield off attacks by arrows and gun-shots from the enemy.the dented parts are used to shoot and keep eyes on teh movement of the enemy.

Walled-in courtyards, studded along the gentleslopes inside and outside the great wall,you will find some ruins of the walled-in courtyards.the garrison soldiers at the that time used to raise and keep horses here,they also called by the local people as horse-stables.