The 500-acre Post Falls Community Forest and adjacent 75-acre Q'emiln Park offer numerous hiking trails with many loop possibilities up to about 6 miles, and also rock climbing, picnicking, and swimming. It is located just over the Washington border, in the city of Post Falls Idaho. There are two trailheads, at Q'emiln Park at lake/river level (entry fee in the summer) and up the hill on Riverview Drive (free all year).
The network of hiking trails run through ravines, along the river, and up and down the hillside, connecting the two trailheads, and all trails are blazed with colored circles and diamonds. Trail maps are posted at both trailheads, and can also be downloaded from the Post Falls Parks web site. There are a few places where the trail borders private property, so be sure to stay on public land by consulting your map.
If you want a flatter hike, start at Q'emiln Park (although some up and down will still be required). If you start at the Riverview trailhead, you will initially go down, and then have to climb back up the hill at the end of your hike -- but you will be rewarded with views of the valley.