We will be in Barcelona at the end of July and were thinking of spending a night in Carcasonne on our way to Avignon. Does anyone know how long of a train ride that would be? Or is it best to spend an additional night in Arles or Avignon? Any help would be great!
You can easily find the answer by checking the timetables at www.bahn.de. Click on "Internat. Guests" to view the site in English. If any of the routes shown require changing trains, click on "Show details for all" to see where those connections are. Be aware that you may find it helpful to make two timetable searches, one departure from Barcelona Sants and one departure from Barcelona Franca.
I liked Carcasonne very much, but not everyone does. If you go, the overnight strategy, staying in the old city--which gives you the night and the morning without the crowds--is the way to go. There is also a tour that is worthwhile because it takes you through some parts of the castle that are otherwise inaccessable.
There is a great deal more to see and do in Provence, so depending on how much time you will spend there you could make the case either way.