Ahhh... the Great Wall...
Have been to it before, but it is still impressive to see again.
Last time around when I was in China visited Mutianyu, this time Simatai. Simatai has a lot less tourists, makes it a lot nicer to visit. It has also been restored less so can get a better feel for what it is really like. Part of it is only a narrow run down path, it's not all like the majestic photos of the restored sections.
A bit further out from Beijing, about 3 and bit hours by bus. Although with the traffic I'm sure spend about an hour of that just getting out of Beijing.
The fun bit with coming off the wall is the flying fox down. Makes for a much faster way to get down.
Think will be getting to see the Southern end of it as head along the Silk Road.