The Great Smoky Mountains has an interesting hike, the Rainbow Trail-Mt. LeConte-Bullhead Trail loop, with a 15-mile continuous loop without backtracking, and has an elevation gain of around 4,000 ft. This trail gives you about the best Smoky Mountain experience you are going to get in one day. There is a lodge at the top.
Another loop, not quite so difficult, is the Spence Field-Appalachian Trail-Russell Loop in the Smoky Mountain National Park out of Cades cove. This is about 14 miles, but does not have the elevation gain or the lodge on top. It is around 30 miles west of the LeConte section.