Rec’s for Nice and/or Paris?
Have 3days / y6days respectively, 16th thru 26th. Christmas night at Moulin Rouge!
Can't help you with Nice but Paris:
If you're into museums and sights, GET THE MUSEUM PASS AT THE AIRPORT. It serves as a ticket to most of the big name spots and is invaluable because there is usually a seperate line for the museum pass that has no one in it. If you've traveled all the way to Paris you don't want to spend any time standing in line, trust me.
Louvre is worth going to but pick your best 8-10 sights beforehand, make a beeline to those, and get out. See:
https://www.walksofitaly.com/blog/paris/things-to-see-in-the-louvre There is more art and history in the Louvre than you could appreciate if you went there every day for a month. You just need to pick your needs, see them, and get to a museum that's less crowded. Speaking of which: Mussee D'Orsay is a great museum for seeing some excellent art and is much less crowded and stressful than the Louvre. My personal favorite spot though the
Musée de l'Orangerie. It's main draws are Monet's Water Lillies, which were painted with this space in mind. 10/10 experience sitting on those benches and watching the paintings change as the lighting from outside changes with the weather.
Champs Elysees is worth seeing. Arc De Triomph is at one end of it, and you can climb to the top and get an awesome view without waiting with your museum pass. Notre Dame was obviously worth seeing, though I'm not sure of its state at the moment. Still, the area it is in is very cool, and there are some incredibly old Roman ruins underneath the square that Notre Dame sits on, which are cool to see.
Eiffel Tower is beautiful. Bad news: You are probably too late to reserve a trip to the top. Good news: You aren't missing anything. The view of Paris is better with the Eiffel Tower
in it. Arc De Triomph has a better view.
Take a cruise on the Seine if it's not too frosty.
Eat all the bread, pastries, and macaroons. Drink all the wine. Drink all the champagne. Get steak frites at Le Relais de l’Entrecôte. Go to Harry's New York Bar and get one of the cocktails that was invented there.
Warnings: Like most big European cities, pickpockets are real. If anyone you don't know starts to approach you with a sob story, they are probably trying a scam. Watch your space with them, put your hand up and shake your head to indicate that you aren't interested and keep walking. Watch your wallet.
You will have to wave down your waiter or waitress at restaurants. They think coming to you with the bill after your meal is being pushy, so don't be shy to get their attention. I felt bad doing this at first but grew to enjoy it because it meant I could end the meal anytime I wanted.
Something I think is big:
Try to speak French to people. If you start off by trying to speak in their language, then ask them if they can speak English once the conversation has left your grasp, they tend to be more polite. "Bonjour" "Ca va?" "Je voudrais..." and "parlez vous anglais?" is all you need. I think showing that you are making an effort to engage the culture tends to charm them. I never had a bad experience with anyone in France and I tend to credit my bad attempts at French with this.