Couple visiting for 3 weeks (End of March/Beginning of April)

Hi,

I've read some posts from this subreddit to get an idea but was wondering what suggestions people would have. My girlfriend is huge on art & culture, I'm big on history & nature (ie volcanoes, lakes, etc), and we're both interested in trying different foods, markets, and experiences. We're going to be flying into Rome and flying back out from there.

We're definitely interested in visiting Venice, Florence, Milan, Rome, Sicily, Amalfi, Verona, Naples, but we want to not be rushed so seeing all of them isn't necessary.

Thanks in advance!