The Boulder River trail is a nice mellow hike along a river through and old-growth forest. It's a perfect winter hike -- not just because of the low elevation, but also because it gives you a huge dose of vibrant green color.
The trail is just an hour and a half from Seattle, and incredibly easy to get to. We got to the trailhead about 10:30, and only three other cars were parked there. As we began hiking, it became immediately apparent that this was going to be a very wet, muddy hike. Numerous tiny streams
After about a mile you hit the first waterfall, and after another half mile, the second. There's a nice spot down from the trail to take a lunch break. This would make a money picnic spot! After that the trail has a little more up and down, but nothing close to intense, and it has a few slippery scrambly stream crossings, but these are also nothing intense.
The trail passes a couple camping sites, and at about four miles, ends at a big riverside campsite. We had lunch here, perched on a small fairly dry birch branch. The river was really loud, and I watched the water rush in white eddys around the bright green moss-covered boulders. We started getting cold after about 20 minutes, so we started heading back.
Directions: From I-5 drive Highway 530 east to mile point 41. Turn right on the French Creek Road FS #2010. Follow this to the road's end at 3.8 miles and an ample parking area. Northwest Forest Pass required.