Take the second feasible train from Mestre to Florence, ideally an early Frecciarossa if it’s available; otherwise a Regionale or a combination service will still get you there in about 1 hr 45 min to 2 hr. From Mestre station, aim to arrive 20–25 minutes before departure so you’re not rushing ticket checks or platform changes, and keep your bags light because Firenze Santa Maria Novella is very walkable from the center. Once you arrive, expect the station area to be busy but easy to navigate—if you have luggage, use the left-luggage service at SMN or just keep things minimal for the day, then head straight toward the historic center on foot.
Start with Piazza del Duomo, which is the best “first look” at Florence: the cathedral, baptistery, and bell tower all sit right there in one dramatic open space. Even if you’re not climbing anything, this is a great 30–45 minute stop to soak in the scale and take photos from different corners of the square. From there, wander toward Mercato Centrale Firenze in San Lorenzo for a late lunch or substantial snack; this is one of the easiest places to eat well without losing time, with plenty of stalls serving everything from pasta and truffle sandwiches to ribollita and porchetta. Budget around €15–25 per person, and don’t stress about being too formal—this is a relaxed, practical food stop, especially if you’re short on time.
After lunch, take a short walk to Piazza della Signoria, Florence’s open-air showcase of history and power, where the Palazzo Vecchio façade anchors the square and the statues make it feel like a museum without walls. This is the best stretch for lingering without overplanning: sit for a few minutes, people-watch, and let the city slow down around you. Then continue toward Gelateria dei Neri in Santa Croce for a final sweet stop before the station; it’s a dependable local favorite, and €4–8 gets you a very good cone or cup. If you have a little buffer, walk back toward Firenze Santa Maria Novella through the center rather than hurrying—Florence is nicest when you keep the pace loose.
Plan to leave Florence around 6:00–6:15 pm so you have a cushion for the walk back to the station, any platform changes, and the usual late-day crowds at SMN. Trains back to Mestre are straightforward, and with an on-time departure you should be comfortably back by 8 pm. If you end up with a few spare minutes near the station before boarding, it’s easy to grab water or a quick snack, but don’t cut it too close—Florence station traffic can move slower than you expect at the end of the day.