Wu Ling Shan

It's not easy to go there, since there is no direct sightseeing bus. We took bus from Beijing downtown to Miyun county (suburb of BJ) and take a long-distance van to the destination. You can take a train to Xinglong (河北兴隆) instead. It's on the borders of Beijing and He Bei Province (mainly in He Bei).

The 雾灵山 forest park is really big. You'd better drive a car or have someone drive a car...
We two walked about 12 kms upward and it's less than half of the total way.

During the weekends, there will be more people. Since we went there on Sunday, there were frightening less people in the big forest park.
Fortunately we met some people from Beijing who happened to visit after their overtime work. They were crazy about driving in such challenging roads full of sharp turns. They were quite kind to pick us up.

We had planned to stay in one of the hotels in the park for one night. But we gave it up, since it seemed we might be the only two who would stay overnight. We went back to Beijing together with the 3 friendly guys that night.

Thus here are my suggestions if you want to hike.
Go there on weekends, instead of weekdays. Friday night, Saturday and Sunday morning there will be more people. Since it is really big, it is far from crowded.