Hi ,
I just got held up by a bunch of rather rude acting cops. As we had no way to communicate, they ushered me into the next town by konvoi and then started, still to no avail , since in Chinese . Then they flashed a little booklet with a paragraph saying, that foreigners are not allowed here.
The town was Huanglong, north east of Xi'an. Reason I found out later about: A high security prison is there.
2000 I crossd China for 5 months. Around Loop Nur in the Taklamakan desert I got fined 50 $- atomic test area.
It's very hard to impossible to find out, which areas are closed.
I would recommend, to stress the fact very much, that you are a tourist. show them your maps, where you cycled from , where you will go... and they will warm up, will let you, go, in most cases, I hope, ahead of me, still.
seb. in China