Yes... a very subjective question...
We will be doing the Rick Steves 15 day "Paris & South of France" tour this coming fall and the tour ends up in Nice. We have an additional 6 days tacked on the end with which to consider doing some additional car/train travel.
We've been to Italy so I don't think we want to jump over the border. The obvious options that we are considering are a) Go back to spend more time in Paris (the RS tour only spends 2 days or so and our return flight is from Paris anyway), b) explore more to the north including Alps, Burgundy, Alsace regions, c) try to zip over to do some of Brittany & Normandy regions
6 days isn't a whole lot of time so we obviously can't do ALL of the above -- anyone (everyone) have suggestions? While I'm sure that we could use up all 6 days just wandering through Paris, is that the best value for our time?