East of North Bend the Snoqualmie River has three forks, aptly named the North, Middle, and South Forks. I-90 follows the South Fork to Snoqualmie Pass, and the trails/mountains off it are fairly popular. Just north of exit 34, you can pick up Middle Fork Road, which will take you along the Middle Fork of the Snoqualmie River. Take this pothole ridden, dirt road 11.5 miles, and you will arrive at the trailhead with ample parking and a restroom to boot.
The trail starts off with a large wooden suspension bridge that crosses the river, giving terrific views upstream and downstream Cross the bridge and head upstream (left) for a 12 mile, low elevation gain, groomed trail that will take you through the woods with excellent views of the mountains and the river. This is an excellent trail for kids. In fact, given the length, the location, and the fact there is some elevation gain (but not a lot) this might be our new favorite exercise spot for the family. Lots of old growth, lots of vegetation, and lots of tiny water crossings.
About 2.5 miles in was a nice water crossing (about 12 feet wide) where we stopped for lunch and used as our turnaround. One day my wife and I will be back to hike the entire length.
I am not clear whether mountain bikers are allowed on this trail or not. I saw lots of bike tire tracks in the mud, but did not see any bikers today.