We are planning for three weeks, perhaps a bit more and don't even have an itinerary yet. I thought this community might be an excellent place to start.
About us: I'll be 61 and my wife a few years younger. We don't mind lots of walking (eleven days in New Orleans for JazzFest and we averaged over ten miles a day). We will be leaving from California. May try to find airbnb or VRBO accommodations (have had good luck with those in Hawaii, Mexico, etc.). Both of us enjoy history, architecture, food, art and wine (not necessarily in that order). Like staying in a place more time to get a feel for the place and make our own "discoveries." Not certain whether we want to drive or use trains/public transit. Our budget is flexible (for the time being), but I wouldn't go overboard! I am certain there will be other questions and I will try to help as you try to help!
Top of our list are Rome, Florence and Venice. We have also been encouraged to possibly see Croatia for a few days. Possible to work in Pompeii? Would like to visit other Tuscan hill towns and the Cinque Terre (sp?) looks like fun. Am I being vague enough? Any suggestions or ideas for how long in each place, etc., sights to see and so forth, as I begin to plan this thing, would be appreciated.