Stelvio sounds always like a great idea. Did it last year, and might be there again today. But thats already planned and only 2 weeks after your date. We're doing this:
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And on the way there we'll start in Stuttgart and drive to Monza, and may very well take a small detour to visit Stelvio again
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Oh anf FYI, If you didn't already know: Stelvio is now a toll-road.