Only 4-5 hours in Florence- what to do?

Tough choice. If art, I would pick Accademia. If landmark, Duomo. Otherwise walking the city is great. There is a great food market in Florence as well.

With only a few hours, I’d stay away from the big museums. Walk the city, cross the Arno for some nice views of Ponte Vecchio and go from there. Time permitting, there are some great sights that don’t take much time to see: Orsanmichele and Medici Chapel spring to mind. Santa Maria Novella is near the train station and contains some of the best/important art in situ. Somehow, it’s a treasure that seems to get less attention than other churches in town. Resist the temptation to get in line for the Duomo or Baptistry. These both come with obtuse ticket procedures and long lines for minimal payoff. Enjoy them from the outside. If you’re hungry, swing through Mercato Centrale for a quick bite and maybe get some goodies for your travels. IMHO, the best, more rustic options are downstairs.

Walk around the city and absorb the Renaissance ... there might be a Medeci around any corner. Look at the (copies of) Gates of Paradise doors on the outside of the Baptistry (no tickets needed.)

Uffizi -- and David in the Accademia and Fra Angelico in the San Marco -- are magnificent, but Florence itself is an art treasure.

WALK! Have a snack and cool drink in the shadow of the Duomo. If you are really interested in seeing specific insides, I suggest you make timed entrance reservations for ONE place (not the Uffizi - you don't have nearly enough time). There really is so much to enjoy on the outside.

We got a reservation to see David and planned around that ... saw the Duomo, Ponte Vecchio and shopped some and had lunch

I think we had about the same amount of time this summer, maybe an hour or so more. We got advance tickets to academia, saw David (very impressive in person), academia is not that large, especially compared to the louvre! The duomo is just right down the street and one of my favorite landmarks in all of italy. We didn't go into the duomo but I would highly recommend at least walking around it. If time permits walk to ponte vecchio and see some of the city, it is breathtaking!

Thank you to all for your recommendations. These confirmed what I was thinking for our time there in two weeks.

I would walk the city, take an ice cream or a small meat at Rivoire’s on Piazza della Signoria and savour the Piazza for 3/4hour. I would then walk to the Piazza del Duomo. You can walk into the Cathedral if you do not intend to go up. You will at least get a small idea of its beauty. Then go to oltrarno and go to Piazza Santo Spirito, Visit the Church and imagine Leonardo da Vinci walking in the area. Mona Lisa used to live in the area.
In the same area is Ponte Vecchio and Pinte alla Trinita. If you come from Santa Maria Novella Station, visit the Santa Maria Novella Church. Another place to visit is the leather market near the Wild Boar sculpture (Cinghiale). Give him a pad, it will bring you luck.
After such a short visit to Florence, you will have to come back

Given a comparable amount of time a few months ago, I visited the Santa Maria Novella church, the Museo di Palazzo Davanzati, wandered around and looked at the Duomo, and ate gelato. It was a good day. I had been to Florence before. I agree that you wouldn’t really have time for the Uffizi, but you could wander around the nearby Piazza della Signoria, and see the sculptures there.

Cross the Ponte Vecchio, if you turn right you'll see a Gelato place, it's been 5 years so things may have changed but they had an excellent cinnamon gelato. While on this side and if you don't mind a bit of a hill walk, head to Piazzale Michelangelo https://www.google.ca/maps/place/Piazzale+Michelangelo/@43.7631469,11.2639205,792m/data=!3m1!1e3!4m5!3m4!1s0x132a53f743663843:0xb4f768e1820d5119!8m2!3d43.7629314!4d11.2650552
Great view and great photo op looking back into Florence and the Duomo.

I would go to Ponte Vecchio and take really nice pictures -- walk around the different shops and eat a gelato. If the line isn't bad at the DUOMO go to the top - you will get amazing views of the city!

Highly recommend a sandwich at Ino, close to the Ponte Vecchio and Uffizi. By far the best authentic Italian sandwich I’ve ever had. They are large, so you can share or save some for a snack later.

David at the Accademia is a must see. No pictures or videos can do justice to this masterpiece. You must see it in person. The rest of the museum is pretty cool too if you're into sculptures especially. And save time for real Gelato. A lot of the places serve fluffy sugary fatty types. Seek out Venchi and Grom. Those are the 2 most recommended. Enjoy!

I would probably walk. Gustapizza across the bridge is a tiny little pizza place that is so good! If you don't mind steps, Piazzale Michelangelo has an awesome panoramic view of Florence.

See the David. It is everything people say and then some.

My first time in Florence was a little less than 6 hours. We saw the David at the Academia, went through the market to see the
Fontana del Porcellino (Boar Fountain), walked over the Ponte Vecchio, saw the exterior of the Duomo and had a lazy lunch. I returned to Florence to do more.

If art is essential to you, then head straight to the Uffizi. It is an incredible museum which needs - IMHO - a good four hours to properly appreciate. If you're willing to take a taste and hope to return, then walk the city. Florence is a wonderful place.

I think I would sit on the curb and cry if I had only that amount of time.