At Shidu, the 'Guilin of the north e.g. scenic karst mountains 90 km from Beijing (take train /bus 917 from Beijing) near Du 7 there's supposingly a 10 km loop trail through the valley that few people take.
You need a good trail description / local to point you the way in order to do this 10 km loop trail. As a result it's a lot less crowded though then other parts of Du 7.
You can also take the ~1.5 km trail & back to the top of the mountain for views, which is well trodden (40 RMB: 2011 info).
FYI - I've never been here yet though would like to.
I also found this info:
Hiking/Camping Potential: The Pu Du Resort, about a mile past the main attraction area of Shidu, offers some excellent hiking and scenery. The Pu Du resort itself is a fairly new (opened in June 2001), modern 2-star hotel at the base of a network of miles of well-maintained, well-marked hiking trails winding far up into the valley, past goat herders sheds, ancient sea stone fossils, beautiful rock formations and several caves. There is a perfect camping spot 15 minutes up the trail at the ruins of a goat herders shed. The area around this shed is flat, open and has enough room for a number of tents. Continue up the main trail for several more miles and you will reach a spot high in the valley with a series of raised plateaus stair-stepping upward. These are perfectly flat, free of brush and would be ideal for camping. There is a water source along the lower part of the trail, none higher up.