For years, I was wary of trail biking. But then I tried Riverfront Park. The park is full of winding trails that are never too packed, and you never know when you'll turn a corner and encounter a beautiful view of the Yellowstone River. I'm no impressive cyclist, but it's a wonderful weekend pastime, and Riverfront Park is the perfect place for such an adventure.
For those not interested in taking up cycling, Four Dances Recreation Area has incredible views of the city, a tough vertical hike down to the river and barely-blazed trails, which makes for fun exploring along the riverbank.