As a couple, Rialto Market (Pescaria & Erberia) works.
Get there before 9am and the Pescaria fish hall and surrounding produce stalls are pure working Venice — lagoon seafood, moeche soft-shell crabs in season, vendors shouting, and bacari pouring an early ombra. The catch: the fish market is closed Sundays and Mondays and winds down by late morning, so a midday visitor finds shuttered stalls and wonders what the fuss was.