For a breathtaking yet enjoyable ride through the Langedoc-Roussillon area (just southwest of Provence) , try taking the "Petit Train Jaune" or "Little Yellow Train" through the Pyrenees mountains from Villefrance de Conflent to Mont Louis. The 63km route is open all year. Its a fantastic ride ( unless you are afraid of heights!) through 15 tunnels or so and over 2 major bridges. The scenery is absolutely breaktaking at almost every turn. If you have a France Rail Pass, it does cover this ride. Picnic at the top before your return ride.