Where exactly in China is the great wall?

This should help:
http://www.panasianbiz.com/wp-content/uploads/2008/12/china_great_wall_river_map.GIF

If you would like to visit the Great Wall. I think the most well kept segment of the wall is near Beijing. there are plenty of tours that go up there, but beware of the scammers in Beijing that solicit such tours especially near Tienanmen Square and the Forbidden City. I remember being in the forbidden city and seeing one woman ask me if I would like to go on a tour, me and my friend turned her down. The next day we went to the great wall through a tour offered at our hostel. Dragon Inn Hostel. Was completely worth the money because we encountered the woman who was soliciting tours of the great wall the day before in the forbidden city. While we were at the Great Wall. She had two Americans with her they were shocked to see me and my friend me being american my friend being canadian. Anyway when the two american tourist were exploring the wall. The woman that was the tour for them came to us since she saw us from yesterday, and asked my friend in mandarin for directions, and when he and I didn't have the answer she needed, she left the wall, and left the two american tourist (a mother and her son). It was quite messed up because she charged them 500 RMB, we only paid 120 RMB for our tour, and it was quite organized because the hostel had covered a lot of the expenses we didn't have to worry about. Anyway just wanted to warn you when visiting China these things can happen and in fact this is common in any developing country.