In Beijing area for a month

Hi everyone,
I am a German researcher who is currently staying in Changping just north of downtown Beijing. I will be here for a month and I am hoping to find some tips for my stay in the area.
At the moment I would be especially grateful for some advice on places to visit over the May holiday next weekend. I will have three days off (Sunday to Tuesday) and was thinking to head into some of the mountains around Beijing for a night or two. I normally live in Scotland and would love to get to some scenic area where I can do some light hiking and generally relaxing in natural surroundings.

Many thanks in advance!
Daniel