It's tough to beat Forest Park in Portland for it's easy accessibility and beautiful, restorative forest. We love this hike along the quiet NW section of the 30-mile Wildwood Trail, which has the added bonus of great views down Firelane 15--especially on clear days.
You can access the trail from Skyline Blvd. where it intersects Firelane 15, shown on the map. It's a pretty ridge with views down to the Willamette River and beyond to Mount St. Helens if it's clear.
Walk down the hill through the gate and it will take you into another opening in 1/2 mile. Continue along the trail into the woods. You will pass Miller Creek and it will lead you to Firelane 12 and the Wildwood Trail.
There are a few options at this point, but if you'd like to do a loop hike, one option is cross the Wildwood trail and continue until you you reach Firelane 12. Rurn right up Firelane 12 and follow it to BPA Road (really another wider trail, like the firelanes). Turn right on BPA, then turn right again on Wildwood to take you back to Firelane 15. Then you can follow it back up to Skyline Blvd. Along either route, watch for the 'lil trail off to Kielhorn Meadow, a grassy opening in the forest where you could have a picnic and/or spot wildlife such as birds, deer, or even elk.
When we were last in this part of the forest in mid-March, when it's often pretty damp in Western Oregon. Firelane 12 was somewhat muddy and my ankle was still recovering from a sprain, so we chose to skip the loop hike and simply hike along the Wildwood and turn back after a couple miles. By that point the time on the lovely forested trail filled with native plants like ferns, salal, and trillium, the exercise, and the enjoyable company of our friends Julie, Ross, Noah and Zora (shown in the pic), had down the trick for my wife Krista and me. :)
View a simple topographical map of the lollipop-shaped loop hike described above: https://www.gaiagps.com/datasummary/track/723c3eb2-b2b4-4dca-ae23-6aa45acd9680/?embed=True
Detailed topographical map from Portland Parks showing all the major routes in Forest Park: http://www.pdxparks.org/maps/natural_areas/forest_park_trail_map_070711.pdf