The Great Wall of China is one of those places that needs to be experienced in order to really understand how impressive it is, on so many levels. Photographs definitely cannot show the feeling of standing on the wall and seeing its towers half hidden in the smog on distant mountaintops.
It's big. And it's old. Or rather, some parts of it are. Some parts are fully "unimproved", in that it is as it was, all a bit tumbledown with bits falling off here and there. This is what you can see in many of the photos here. There are other areas in these photos that show "improved" areas, which have to varying degrees been rebuilt. Apparently there are some parts of the wall which are effectively just reconstructions.
It was a real privilege to see these less visited areas of the wall. Seeing the wall snake back and forth through the barren winter landscape and knowing that it was built nearly 1000 years ago inspires a certain amount of awe. It is certainly a place everybody should visit if they can.