To ride from Bologna to Florence in 2 days, you can take La Via Degli Dei.
This is a traffic free ride, travelling through parks and cycleways.
There are different routes depending on your distance preference, and each option is clearly signed.
You will visit beautiful Tuscan villages of Sasso Marconi, which includes the tomb of Guglielmo Marconi, the pioneer of long distance and telegraph radio.
Also not far from the route in the Monte Sole (Sun Mountains), near Marzabotto you can find the second world war historical location where the German SS massacred 770 civilians. This is the place where the Italian resistance fought for liberation from the Nazis. There is a memorial to be visited. If you are in the region in November you can see the annual festivities.
Sampling Italian food and Tuscan wines as you go (but of course not too much!), the Tuscan countryside is truly stunning and is best appreciated from the saddle of a bicycle.