The Columbia River Gorge has an overwhelming wealth of wonderful hikes. With all the elements of a quintessential Gorge hike—a climb that gets your legs burning and your heart rate up, a meandering trail through old growth forest, a gorge view, and several waterfalls—the Wahkeena-Multnomah loop (5.2 miles) is one of my favorites.
You can start this hike at either end, but I like to park in the Multnomah Falls parking lot and walk down the road a short ways to Wahkeena. The scenery never quits on this hike, as you start with a waterfall, pass at least two or three in the middle section (I lose count), and finish at the most famous falls in the gorge, Multnomah.
You'll meet up with the crowds as you hit the switchbacks coming down from the top of the falls, but if you avoid summer weekends, the first four miles should provide some good quality time with the nature around you.