What's a good 3-day itinerary for Paris?

Start at Sainte-Chapelle when the doors open at 9am. The upper chapel's stained glass catches the morning sun from the east — thirteen panels of deep blue and crimson that make every other church window in Paris feel like a rehearsal. You'll smell the cold stone the moment you climb the spiral staircase. Give it forty-five minutes, then walk across to Notre-Dame. The cathedral is still under restoration, but the exterior and the parvis are open, and Île Saint-Louis is a five-minute walk east for a scoop at Berthillon — the pistachio is the one to get. Cross to the Left Bank via Pont de la Tournelle and duck into Shakespeare and Company with its creaking floorboards and the smell of old paperbacks stacked floor to ceiling. Lunch at Bouillon Racine on Rue Racine: Art Nouveau tilework, three-course formule around €20, and the blanquette de veau is what your grandmother would cook if she were French. Walk it off in Luxembourg Gardens — the metal chairs by the Medici Fountain are the best free seat in the city. The whole day stays inside a one-kilometre radius. That's the point.

The Louvre will eat your entire day if you let it. Don't. Pre-book a 9am slot, enter through the Passage Richelieu on Rue de Rivoli — not the pyramid — and head straight for the Denon wing: Winged Victory at the top of the stairs, the Grande Galerie's Italian paintings, the Mona Lisa (smaller than you expect, behind bulletproof glass, ringed by two hundred raised phones). Three hours is enough. Walk through the Tuileries to the Orangerie by noon for Monet's Water Lilies — two oval rooms, almost silent, the canvases curving around you like being inside the painting. It takes forty minutes. Lunch in the Palais Royal arcades, where Café Kitsuné does a good matcha and croque-monsieur for about €16. Cross the Seine on Pont Alexandre III — all gilt and cherubs, the most theatrical bridge in the city — and spend the afternoon at the Musée Rodin. The garden alone is worth €13: the Thinker outside, rose beds in late spring. Eiffel Tower at sunset with a pre-booked second-floor ticket. Skip the summit unless visibility is clear; the second floor gives the same panorama for half the wait.

Morning in the Marais starts quiet. Place des Vosges at 9am still has dew on the grass and almost nobody there. The Musée Carnavalet next door is free, covers two thousand years of the city's history, and takes about ninety minutes — the room recreating Proust's cork-lined bedroom might be the strangest thing you see all trip. By 11:30 you'll be hungry. Rue des Rosiers is three blocks south. L'As du Fallafel has the famous line; Mi-Va-Mi across the street serves the same quality without the twenty-minute wait. Get the special with aubergine and eat it standing on the pavement like everyone else. Take Metro 11 to Châtelet, then line 4 to Abbesses. Walk up through the vineyard side of Montmartre where the crowds thin out fast. Sacré-Cœur's south-facing steps give you the whole city skyline. Inside smells of candle wax and cold marble. Dinner at Le Bouillon Chartier on Rue du Faubourg Montmartre: a 19th-century workers' canteen where waiters still scribble your order on the paper tablecloth, and a full meal runs about €18.

A few things most first-timer guides skip. The Navigo Easy card is the right transit pass for three days: load ten t+ tickets at any metro station for about €16.90 and tap as you go. Paris walks flat everywhere except Montmartre, but the cobblestones on the islands and in the Marais are hard on thin-soled shoes — wear something with structure. Restaurants serve lunch from noon to 2pm and dinner from 7:30pm onward. Arrive at 7:25 or at 9pm; showing up at 8pm means every table is taken. April mornings tend to sit around 8–10°C with a damp chill that burns off by noon, so layer with something you can stuff in a daypack by afternoon. The coffee is strong and comes in a small cup. Order un allongé if you want something closer to a long black.