If you only have time to visit one walled town in France then I would choose Carcassonne. The town is in great repair and lots of the buildings are now shop fronts however the castle has not lost it's original feel. We visited many buildings and they are all in excellent condition. I had a particular interest in this town because I have been a bit of a follower of the Temple Knights and their history is closely associated with this town. But this is not the reason I am recommending it to you, I was really impressed with the way this town had been maintained, the height of it when you look down on the new Carcassonne town gives you an understanding of the importance of position in these days gone by and also just too keep all us tourists happy there is a great range of shops to visit. A must see.