My husband and I are driving from Italy to the French Alps next September (we'll collect and return our hire car in Italy) so that we can spend some time doing day hikes in the Parc des Ecrins and de la Vanoise. We plan to spend 5 nights in each national park, probably in Val d'Isere for Parc de la Vanoise and in Les Deux Alpes for Parc des Ecrins.

In between these two hiking stays, we'd like to see a little more of the Rhone-Alpes area. We're currently thinking of a 3 night stay in Vienne so that we can do a day trip to Lyon by train, and then another day trip to Ambronay Abbey and Pérouges by car. We've previously spent time in the Auvergne, so are not currently thinking of going that far west again this trip. We do intend to spend a day in Grenoble and also to visit Vizille on our way from Vienne to Les Deux Alpes.

Is there something that we're missing in the Rhone-Alpes area, though? We'll have 6 weeks for the total trip, and will be spending a fair amount of that in Italy, but we do have some flexibility to extend our French stay a little.

Your plan looks perfect. I suppose you know, that Vienne is full of Roman stuff (on both sides of the Rhone river).
Perouges is charming, but there is much more to see and to do at Lyon.
September is no longer high season, check opening hours and timetables of cableways, etc.in the parks.

Thank you so much, neckervd. I'd also like to acknowledge the wonderful advice you've offered us in relation to our previous trips over several years now - so much appreciated!

Yes you should visit the Ardeches or head back to Auvergne and hike around Puy du Dome!

Depends what you like, but here are some spots we enjoyed:

Caves: Grotte de Choranche, La Balme les Grottes

Photogenic: Crémieu, Le Palais Idéal du Facteur Cheval in Hauterives, the hanging houses of Pont en Royans, Sainte Antoine l’Abbaye, Chanaz

How sporty a driver are you? We were recommended the balcony road of Combe Laval near Saint Jean en Royans but ended up admiring it from below, not being sure of ourselves with the manual shift rental car. The Vercors in general is terrifically scenic, but then, you’ll have been in the Alps….

Obviously Lyon itself would reward many days’ visit but again, depends what you like.

Thank you, touringtimothy! We agree that the Puy area is magnificent: we based ourselves in Murat for a week and walked the area. Stunning!

Thank you, FTOttawa. These are all great suggestions, and since my husband is a keen driver, we'll definitely explore some of the more adventurous options.