The Oltrarno is the half of Florence that kept its workshops, and Santo Spirito is its living room — a square that does business in the morning and turns sociable at dusk, with the city's plainest great church watching over it. Do this one early, before the chairs come out.
Under three kilometres, walked east toward the river. Start in Piazza Santo Spirito with a coffee and the blank facade of Santo Spirito in front of you — Brunelleschi's last design, and the clearest place to read his grid of grey pietra serena columns. Go in; it costs nothing and it's nearly always quiet.
Then east along Via Santo Spirito, where gilders and restorers still work behind open doors, the artigiani (workshops) the street is named for. Slip down Via dei Velluti, the old velvet-weavers' lane, then on to Santa Felicita for Pontormo's Deposition — acid pinks and blues, just inside the door, usually yours alone.
End where the lanes meet the river at Ponte Vecchio. Don't cross it; just take the approach, then carry on into the centre over the next bridge along.