The Durrance Loop is a great place to jump on your fat bike and take a winter ride just north of Ketchum, Idaho. Most of the trails in the Blaine County Recreation District's massive system do not allow bikes on their courses, so finding a place to ride can be tricky this time of year. The trail is mainly frequented by cross-country skiers and their lucky dogs; there is no snowshoeing here, and fat biking is still catching on, so you won't see many other bikers. Dogs can safely run alongside through the wide open and flat terrain, which is a great perk of this particular trail.
One of the few other nearby winter bike options is the Wood River Trail in town. The Durrance Loop is much better suited for an athletic and uninterrupted ride, however. The ride is not challenging overall, but it is a pretty area and it has a mellow vibe. A few quick laps could be an easy way to stay in biking shape throughout the year if you are looking for a workout, but casual riders can also enjoy a slower single lap. The Wood River Trail is more dynamic and has more options, but the Durrance Loop allows you to throw on your headphones and avoid the cars at multiple crossings and intersections that come with rides in town.
There is a large parking lot that also serves the North Fork trails (cross-country and snowshoe only) and the Sawtooth National Recreation Area Visitor Center. This is a popular spot thanks to its proximity to Ketchum, multiple trails, and facilities. You will need a day pass, which you can get at the visitor center, or an annual pass, which you can purchase online.