I didn't know about this place until Erik's friend Tom, whom we would be staying with the next two nights in Seattle, told us. We would be on our way up to Issaquah where Erik would spend a day working in their office there and Capitol Forest would not be too far out of our way. We took the suggestion and drove out to Mima Falls Trailhead (near Little River off I-5). The planned route was: we follow Green Line #6 to Fall Creek Campground and then take Mima Porter #8 back.
There is a huge map at the trailmap, of which I took a picture that turned out to be very helpful later on. Over all, the trails are well marked. There is one fork where we sorta ignored the stick that lay across one trail and took it, which took us off Green Line #6. It took us down a singletrack (muddy at spots) that ended on some forest road. Following the map in my camera, we took some forest road riding and eventually found our way back to Green Line #6. If we had followed the correct trail, the entire route should have been pretty much all singletrack. When we rode it, some sections were dusty so I had to wear a bandanna across my nose when I followed Erik, but over all, we were mostly in a dense forest and the riding was very meditative (not very technical). Erik said it reminded him the woods he grew up in.
The trails seem to be very popular with equestrians as there were many horse trailers parked at the trailhead when we arrived there on Sunday afternoon. But on the entire ride, we only encountered one horseback rider and no other mountain bikers. There was a rifle range close to the trailhead so we could hear gun shots, but that was really nothing to worry about.
For our GPS track (including the off route section), click on Trip Details below: