Varenna is on Lake Como and is only about an hour (maybe less) by train. Great restaurants in that town, Milanese will go up just for lunch. You can take the ferry to Bellagio (and other towns) no need for a car. Very easy day trip.
Forget Florence. Not sure how far Turin is by train.
Bergamo is under an hour and a good day trip. But Milan is underrated, easily worth a few days.