There are some great opportunities along you're route. First of all I would go back to Girona or even Barcelona. Both are very interesting cities. From there you can go on to Andorra. In Andorra you can't do a lot of things, but hey your country-counter will increment by 1. If you're into mountains/hiking you can spend some time there. From Andorra I would go to Carcasonne. In Carcasonne you can visit the beautiful castle, the Canal du Midi or a old cathedral.
The next stop I would make in Beziers which is also a beautiful city with an old cathedral.
From there I would follow the cost line and stop in places like Cape d'Age, Nimes, Montpellier or Marseille.
Now it depends a little bit if you want to start in the south or east of Switzerland or in the west or Northern part.
If you're going the southern or eastern part I would follow the cost line a little bit more and visit Nice and Monaco.Then I would visit Turino or Milan and finally entering the beautiful southern part of Switzerland, Ticino. There are a lot of nice cities, like Lugano, Locarno or Bellinzona:
But you will also find some interesting small villages in the mountains like for example Bosco Gurin. From Ticino you can cross the main part of the alps via the Gotthard and then arrive in central Switzerland, for example Lucerne:
If you want to start in the northern/western part of Switzerland i Would go from Marseille to Grenoble and then from there to Geneva, Lausanne, Fribourg, Berne to Zurich.
I visited all the cities a mentioned here and I can really recommend it.