DeLeo Wall - Cougar Mountain
A fun hike, with great views, this one is close to the city and very doable for the little legs.
I did this route as a run this week and it was fabulous. Rolling ups and downs, swamps, creeks and even a geocache along the way. The grande finale being a lovely sweeping view to the south amidst a strange and fascinating grove of madrona trees. (I could be wrong, but I think you can probably see Mt. Rainier when the clouds are cleared).
This region is woven with trails, and there are a couple different ways to get to these gorgeous views. The standard trail is a little over 4 miles. But if you have a day to do some exploring, you could spend it wandering the Cougar Mountain Regional Wildland Park. It's fabulous. Waterfalls, wildlife (I literally saw a cougar once!), and all manner of trails, with regional history mixed in.
I especially love this area for trail running because so many of the trails have ups and downs, and can be linked up for anywhere from 2-20 mile lengths. Plus you can find peek-a-views like this beauty...