Four days is the sweet spot for a first visit to Paris, turning a sightseeing sprint into an actual holiday. Days one to three cover the essentials without rushing: the Eiffel Tower, Champs-Elysees, and a Seine cruise; the Louvre, the islands, Notre-Dame, and Sainte-Chapelle; then Montmartre, the Musee d'Orsay, and the Marais. Day four is the release valve, a Versailles day trip to the palace and its vast gardens, reached in 45 minutes by RER C and best started at the 9am opening on any day but Tuesday. This length suits travelers who hate the forced march, couples, and anyone whose flights bookend the trip awkwardly. For four days we recommend basing in the Latin Quarter: it is central and walkable to the islands and the Orsay, offers better-value beds than Saint-Germain next door, and sits on the RER C line straight to Versailles. Beyond four days, add a Musee Rodin and Invalides morning or run on to Amsterdam by fast train in about three and a half hours. Book the Eiffel, the Louvre, the Orsay, and the Versailles Passport well ahead.