Travel itinerary for 3 weeks from French Riviera through spain

I did both northern Spain(this summer, + a week in Barcelona back in october) and a full trip to southern spain in 2015.
Eventhough I very much enjoyed Barcelona(fantastic city), the Pyrennees, Basque country, Picos de Europa, Leon, Burgos and Madrid, no doubt in my mine, Andalusia has something so unique. The architecture, the pace of life, the atmosphere.
Cordoba, Sevilla, the white villages, Ronda, Granada, just to name a few(we had a car, so we explored also outside this top places), all of them have a very special place in my heart.
As far as the French riviera, it depends also on what you like.
The classics would be Nice, Monaco, Cannes, etc.
I personnally have a preference for smaller towns, authentic places, nature, history, architecture,etc.
If this is what you are into, move west just a bit to Provence, between Cassis's gorges, to Aix-en-Provence, Arles, Avignon, Orange and Pont du gard(bridge) for roman pieces, Nimes, The Ventoux Mountain, Verdon Gorges, small villages like Roussillon, Gordes, Les baux de Provence, etc.
So many things to see there...
Have a great trip.
Claude

Both northern and southern Spain are worth seeing, as each is completely different from the other. Since you’ll be north (if you do visit the Riviera), see northern Spain and save the south for a couple other trips. As I’ve stated in other threads, one could spend a couple weeks in each of Span’s regions and still not see everything they have to offer.

What are the specific dates of your trip? Barcelona and the Catalan coast should be pleasant at least through October. The Basque Country is better in the summer, when its weather is mild and a bit rainy while the rest of Spain swelters. The Pyrenees in the fall--I just don't know.