Florence in two days
All tourist attractions are within a stone throw if you diligently cover by foot. For someone like myself to soak up the local arts fraternity, culture, history and gastronomical treats, its a worthy trip. To stay longer to appreciate would not appeal as much, probably better if you are into arts and architecture.
Insider Tip:Do not fall prey to tourist traps, via signing up indemnity forms by people touting as NGOs or welfare organizations. As well as not allow strangers to take your photograph.