Walk around the cathedral precinct and Île de la Cité to see restored facades and historic bridges; exterior access and surroundings open all day (interior access limited after restoration).
Major collection of Impressionist and Post-Impressionist masterpieces in a converted railway station; plan 2 hours to see highlights (Monet, Van Gogh, Degas).
Walk through the park for classic views and photos; if you plan to go up the Tower, pre-book timed tickets for June to avoid long queues (open 9:00–midnight in summer).
One-hour commentary cruise departing from near the Eiffel Tower offering a relaxing overview of riverside monuments; cruises in June run frequently until evening.
Museum of non-European arts near the Eiffel Tower showcasing global indigenous art and design; check exhibitions—open typically 10:30–19:00 (closed Mondays).
Stroll down to Pigalle to see Moulin Rouge exteriors and the neighborhood's eclectic shops; save cabaret shows for evening bookings if desired (shows often start ~9:00pm).