Gilles - You mention restrictions...not sure I follow. If you're talking about disturbing those who live in the hutong...well..it's not really an issue. They're used to "white" people and all other manner of tourists. The same rules that apply elsewhere in the world apply here as well...be respectful and courteous and they'll let you snap away. Often staring at you and curious, but, not telling you to stop.
Jiu Zai Gou - An absolute pristine alpine scenic place. If you enjoy scenery then it's a must see. It's a little hard to get to...it'd be especially helpful if you speak some Chinese. Even basic things will help. Getting an English tour isn't impossible. I was lucky enough to live just 2.5 hours south of the reserve for 6 months. That area is beautiful and heavily influenced by Tibetan culture.
Other places of note might include: Guilin and Yangshuo in southern province of Guangxi. Also of note and not to be missed if you have a chance is Yunnan, otherwise known as "Shangri-La". I could on forever. If you have an specific questions feel free to send me a message.