As well as the usual Jinshanling or Simatai Great Wall tours, you can also explore other parts which are completely unrestored. Beijing Leo Hostel run a tour/hike to Secret Shen Shui Hu for 100rmb.
It should be noted that you're not always following the path of the wall itself, and if you want to get the 'classic' wall experience (and photos) take another tour instead of, or as well as, this one. On the other hand, you will definitely avoid crowds and hawkers.
Beijing Leo Hostel, Guang Ju Yuan, 52, Da Zha Lan Xi Jie, Qianmen
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