is spread out a bit, but it is relatively straight forward to suggest that you see the Vatican City
, the Colosseum
You did not mention how you plan to move about Italy? I would suggest using Trains for several reasons; Rome is difficult to drive in and parking is not simple. In Venice, they do not allow automobiles, so you would have to leave your car elsewhere - but the train station is in the city.
So lets assume that you should stay in Rome for a minimum of three days, the next stop would be Florence. The city has some fascinating places to visit including museums, the famous Cattedrale di Santa Maria del Fiore
, the Piazzale Michelangelo
, the Uffizi Gallery
, the Ponte Vecchio
, etc. Bear in mind that in Florence, you will not be very far from Pisa, where you could day trip and see the Leaning Tower of Pisa
. For that reason alone, I am going to suggest 4 days in Florence because Pisa is well worth the visit.
The next stop would be Venice
, this is a "pedestrian only city", so be prepared to hike about, or utilize the water taxis. The gondolas are everywhere, but they are expensive. Be sure to plan to visit Lido Beach (requires a water taxi ride), Saint Mark's Basilica
. Remember that Venice is comprised of a number of islands, and that each island has something unique to see - use Google to figure out what else you want to see here.
I'm not so sure that I would recommend Sardinia as your next stop. Once you are in Venice, you could take a train to the Lake Como area and stay anywhere on the Lake. It is a very pretty area, water taxis are the best way to get around there as well.
You did say 10 or 12 days right? So I think the above would fit nicely into 12 days, and you would have to put aside a day to get back to Rome to return home.
Have a great trip and enjoy yourself. We always recommend making a "hit list" of places & things you would like to see/visit/explore, but don't treat that list as a "gotta do", instead treat it as a set of recommendations and have fun !