Caravaggio Hotel

Florence is a beautiful old city and there is plenty of architecture to see and museums and galleries to visit.
Important tip: get your hotel to book advanced tickets for galleries as then you can walk straight in. Even off-season you can otherwise wait for many hours alongside screaming school groups. A trip up to the top of the Duomo (The Dome - over 400 steps though!) is a must for breath-taking views. We spent five days there in April, the temperature was pleasant and it was only cloudy once.
It is a small city so you can walk everywhere and we felt perfectly safe walking home at night as there is always life in a taverna on the corner. The food is the best thing about Italy - simple pasta and meat dishes that are just bursting with flavour and I recommend a Florentine steak between two or more - a huge chunk of steak which is carved for you and just served with bread or potatoes - not for veggies!
We found a good deal on the internet for the hotel which had just been refurbished - the room was reasonable and clean, the only disappointing thing was breakfast which was a simple cold buffet; cereal, cheese, bread etc. but it was fine for the money. I would say you could see everything in three or four days then visit Pisa on a spare day, which is about an hour away.
Highly recommended for a lovely cultured romantic break.