There's something special about market streets in Paris. They don't just have fresh food and flowers but any business you could possibly need. This one, located in the 2e arrondissement on the edge of the 1e, is particularly convenient for visitors as it's so centrally located. Although crowded on a Saturday morning, its ancient charm prevails.
I recommend sitting down for brunch in one of the many restaurants to watch the crowds of tourists and Parisians mingle. Au Rocher de Cancale is especially affordable at 13 euros for a generous and delicious prix-fixe menu.
Then, perhaps you can pick up some honey bread, drop off your dry cleaning, and sit down for one more coffee.
La Rue Montorgueil
Où? On rue Montorgueil from rue de Turbigo to rue Réaumur, Paris 75002
Quand? Tuesday-Saturday, 10am-6pm; Sunday morning
Comment? Metro Les Halles, Étienne Marcel, Sentier