Start with a focused visit to the Musée du Louvre, allowing about 2½ hours rather than trying to conquer the whole museum. Timed-entry tickets are strongly recommended; standard admission is roughly €22, and the museum is generally open until 18:00, with later hours on some evenings—check the official schedule before setting out, especially as today is already underway. Enter through the glass pyramid if your ticket specifies it, and choose a small route around highlights such as the Mona Lisa, Venus de Milo, and Winged Victory of Samothrace. From central Paris, use Metro line 1 to Palais Royal–Musée du Louvre or line 7 to Pyramides; allow extra time for security.
After the museum, walk directly through the Jardin des Tuileries toward Place de la Concorde, taking around 45 minutes at an easy pace. This is a good moment to slow down beside the fountains and chairs rather than rushing onward. Continue by Metro line 1 from Concorde to Franklin D. Roosevelt, or walk roughly 20 minutes to Café de Flore in Saint-Germain-des-Prés. Expect €20–€40 per person for coffee and a light meal; it is atmospheric but famously expensive, so order simply and settle in for about an hour. From there, take Metro line 4 from Saint-Germain-des-Prés to Cité, then visit Cathédrale Notre-Dame de Paris. The exterior is beautiful in the evening, while interior access is free but subject to opening hours and reservation availability—check the official booking system rather than relying on walk-in entry.
Finish with a 45-minute stroll along the Seine riverbanks near Pont Neuf, crossing onto Île de la Cité or walking toward the western tip of the island as the lights come on. The riverside paths are free and usually lively after sunset; keep valuables secure around crowded viewpoints. If you still want something afterward, the nearby Latin Quarter has plenty of late food options, but the best ending is simply to linger by the water and watch the illuminated bridges.