Unique experiences of southwest Europe

Not totally unique but - while you can rent kayaks, etc. for rivers & lakes in the states, you can paddle one on the Dordogne and drift past medieval castles and some of the most picturesque villages in France. Pull over and have a splash as well. You can do the same underneath the breathtaking Pont du Gard over in Provence.

Help out with the grape harvests.

You can help restore a medieval village - La Sabranenque - in Saint Victor la Coste.

" rough plan goes northeast Spain, south coast of France, north Italy, Switzerland, and Bavaria"
You really should get on Mapquest or GoogleMap and see how far it is between these cities and regions. Spain and France are very large countries if you're going to be traveling on the ground.
We prefer to travel in straight lines between cities that complement each other well. You could easily travel from Venice through Northern Italy (Dolomite Mountains) through Tirol (Austria) and into Bavaria (Munich.) But Switzerland is out of the way, and it's very expensive to travel in.

You could possibly catch a budget flight over to the northern coast of Spain. You might be better served saving France and Spain for your next trip.

If you have an interest in food or wine, you could try going to a harvest festival - in Italy, there are fairs and safer for just about any product from artichokes to truffles.

This is further north in France than the Mediterranean and spreads from Northern Spain to the French Dordogne: -visit the Cro Magnon caves and rock shelters to see the 15-25,000 year old cave art. Visit medieval troglodyte communities. Stay at a farm inn. Seek out unusual carvings in romanesque churches. This isn't terribly unique as thousands of tourists come to see these yearly, but you won't find these in the US.

Troglodytes and carvings aren't restricted to these areas by any means.

Walk the Via Appia near Rome, an almost 2000-year old road. Hire a boat and do the canals in central England. Get a bicycle and do the Donauradweg. Go on a ferry and travel between the Greek islands. Get your shoes and walk below sea level in the 17th-century land reclamations in the Netherlands.

There are so many unique things to do in Europe. Unless you find that walking is walking and cycling is cycling, and it's irrelevant where you do it.

The most memorable experiences from your trip will be unplanned things that just happen. Even the most mundane things you do will be unique because you are doing them in a foreign country. On a long trip I stop at a laundromat and the last time in Italy was a lesson in how maybe some other countries do things better than at home. I found the laundromat to be as interesting as many of the churches we visited. Boring and a waste of time for some but an interesting experience of daily life and I had clean clothes!

Point is don't try and force it with things that might seem unique until you realize that nothing is unique and tons of tourists have done it before you. Plan for the big stuff and the unique moments will happen although you won't realize it till afterward.

Richard, you hit the nail on the head. The unexpected can give you that unique experience and are many times the icing on the cake.

But nevertheless you can do the last bit of the pilgrimage walk to Santiago de Compostela in northern Spain or mud walking in the Wadden Sea and fierljeppen in Friesland, both in the Netherlands, La Tomatina in Buñol near Valencia, playing with bulls in southern France, loads of local sports, etc.....

This General Europe forum is a fine place for your question. (Repeating it for each country is not preferred.) I find Rick's guidebooks quite readable and descriptive, making it easier to get inspired about the regions you've selected. Whatever is tallest, oldest, fastest, traditional, etc, will be covered, as well as his star-rating system helps you to make distinctions.

In the Switzerland book, look first at the chapter on Gimmelwald and the Berner Oberland. That's Rick's favorite Alpine base, with a good combination of local character, sporting activities, and spectacular high-mountain access. You can take the gondola lift to the top of the Schilthorn with a 360 degree view at 9,748 feet and the train to Jungfraujoch at 11,333 feet. I personally would not choose to experience these heights and views through bungee-jumping, para-gliding, or the Via Ferrata (p. 169), but the contact info is there if that sounds more special to you.

I'll add another vote for Cro Magnon cave art to be among the oldest and most special sites I've experienced in Europe.

What David said. I may have missed it, but I didn't see how long your trip will be. Some of the places you listed are pretty far apart, requiring long train rides or flying if your time is short.

I'm glad you qualified the locations you're concentrating on. When you said "southwest Europe," I immediately thought Spain, Gibraltar, Portugal and a little bit of western and southern France.

Go a tad further east and you can take lessons in Яussian Tank Driving just outside of Budapest. My spouse had a blast.