It's quite a hike from Rome to Florence for example and the terrain is quite mountainous. You could try plotting the route like this though.
- Go to Google Maps - Rome
- Top right of the map, click the "Terrain" link so that you can see what the terrain looks like.
- Then click the "Get Directions" link top left in the menu. Rome will be showing already in the bottom field, so type: "Firenze" (without quotes) in the field above that and then change "By Car" to "Walking" (it doesn't have a "Cycling" option).
- Finally, click the "Get Directions" button which will plot the route on the map.
You'll see it's 281km and will take you two days and ten hours to walk the distance. I don't know if Google expects you to do it without any sleep though.
In any event, it'll serve as a rough guide of how long it's likely to take by bike.
I would imagine that any tourist office in Rome would be able to tell you where you could buy a secondhand bike.
P.S. "Firenze" is the Italian name for Florence.
[ Edit: Edited on 30-Apr-2009, at 06:27 by Blinq ]