The Great Wall of China (as I am sure you know) is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China.  Built to keep the nasty little barbarians out.
The bit we went to is the Huangyaguan Pass which was built during the early Ming dynasty and then rebuilt several times.  It was restored in 1984. 
Although very obviously not original it is very impressive and we had the place more or less to ourselves.