It depends on what kind of trip you want to have, your budget, means of transport you want to use.
If you can give us more details you will receive more comprehensive info, however, my suggestion is not to miss main cities of artistic interest as Florence, Rome, Venice, but, above all, I suggest you should focus on a more narrow area to get deeper into things, people, landscapes, flavours, feelings.
Take Tuscany for example: you can visit Florence, but Florence is not the countryside and you will hard be able to avoid touristic places to really taste this beautiful land. Crete Senesi, Mugello, Maremma are beautiful and wild areas that are more Tuscany then Florence.
As AJF I would add Amalfi Coast, no doubt, but if you are going to land in Milan you are going to spend most of your precious 12 days in train. If you choose to stay in the South, well focus on the South, you have got plenty of choices for your visits.
Don't hesitate to ask for further info. Ciao about 8 years ago
Obviously days in Rome for all attractions there, high speed train to Naples - Pompeii, walk up Vesuvius and take a boat trip over to Capri (grotta azzura not to be missed), up to Florence, then Pisa, check out Milan then over to Venice & possibly head south again. Really depends on what you want to see. Take high speed trains if you can afford them, quicker, comfortable & less people. about 8 years ago