If you have been to Italy before and seen some of the major cities and fancy exploring a few places that are easily accessible but not always on the tourist map then Milan to Bologna could be an option.
Landing in Milan will give you quite a few options for flights and will be a good starting point as it is served by the high speed AV train network from Milan Centrale station. There is plenty to see in Milan to enjoy a few days but if you want to see the Leonardo da Vinci’s Last Supper then make sure you book in advance. From Milan you have a range of options but the suggested route would be to take a train to Parma. This is a 1 hour 30 minute train journey as Parma does’t have a AV train station so the journey is slightly slower. If you wanted to see more of Italy then you could break this trip down and stop off at Piacenza on the way getting there in just under 1 hour by train from Milan.
Parma has many sights to offer as well as excellent restaurants but you won’t need more than a couple of days here. There will be some tourists around but in the main it will be locals and students as Parma is quite a big university town. The train station will place you near the centre of the town so if you are travelling light and choose a hotel near the train station you won’t need a taxi.
From here you have a few options of other towns that you can visit which are on the same train line. These are Reggio Emilia, I’ll add this as it is our home town in Italy, Modena and then onto Bologna. Once in this area the train times between each town are quite short and each town is not too big so this will mean you don’t need to do as much walking as you would do in a larger city. A day in each of these towns will be enough time to discover what they have to offer and also give you an experience of being off the usual tourist routes.
From Modena and Reggio Emilia you can take another train and reach Bologna where you can spend a couple of nights. If you want to finish your journey there then you can either take a train back to Milan from the AV station at Bologna or look for flight options from Bologna airport, although these have become a little more limited in recent years. You could also extend your stay and travel up to Venice or travel down to Rimini to enjoy the Adriatic sea. Venice is obviously serviced by its own airport but from Rimini you will need to do a little travelling back to Bologna to get to the closest large airport.
Remember that booking train journeys in advance in Italy means that they are generally quite a bit cheaper. Also staying in a hotel near the train station can save you money on taxis. Also message them ahead if you will arrive before the check-in time to see if they will let you leave your luggage there so you can start exploring the town.
Hopefully this gives you an idea about how easy it can be travelling across north Italy. I remember the first time I came that I was a little stuck at the train station. The self-service machines switch to various common languages and there is often someone who will help you. Many Italians have a good grasp of the English language and whilst it may not be good enough for a conversation it should be enough to point you in the right direction. Also most people are happy to see tourists visiting their local town and will often want to know where you live. When in Reggio Emilia my wife and I often say that I know more people than her as people generally know me as the English man.