The Musée d’Orsay is a wonderful place but be prepared for big queues to get in. We had to stand there for an hour. Also big queue for the cafe.
If you’re going to Versailles, the best way is on the RER-C, one of the regional lines. It has lovely two-deck carriages which give a great view once the train is out of tunnel.
There are several station called Versailles; you want Versailles-Château–Rive Gauche
which is 5 minutes walk from the chateau.
Do not forget the Eiffel Tower. Again , queues can be horrendous to go up, but it’s well worth just walking around. And there’s the Hotel des Invalides just up the road. Also near by is the Val’d Hiver stadium. Events there in 1942 were such that the French police were rebuked for excessive brutality… by the Gestapo.
There’s a lot of history in Paris.
An interesting excursion is to visit the Ile de la Grande Jatte, where Seurrat did his famous painting. You can stand at the exact spot where he stood, and see how different it is today.
Nearby is La Défense, the modern area of Paris, a refreshing change of pace from the 18th and 19th centuries.
It’s a pleasant enough place, but there’s not really much there; mostly tennis courts etc.
Even if you’re not travelling by train, the Gare du Nord is worth a visit. Incredible ironwork, very atmospheric. Many a fictional french secret agent set off from there to do dirty work in London.
A favorite place of ours is the linear park on an old railway viaduct: https://en.wikipedia.org/wiki/Coul%C3%A9e_verte_Ren%C3%A9-Dumont
It runs along the avenue Daumesnil.
My ongoing thanks for all the suggestions - I’ve started a notebook so I can do some planning, including noting what day of the week various places are closed.
Thank you too for specific hotel suggestions, **PatrickLondon ** - that’s my next priority to get figured out and booked.
My friend (who speaks no French) and I (who can say please/thankyou/how much, etc) spent 2 weeks in Paris and never had a problem with rudeness or not being able to converse. We rented an apartment in the 6th, next to Luxembourg Gardens. We bought the museum pass so never had to wait in line to buy tickets. Neither of us had any desire to spend any time at the Louvre, so we did the Louvre Express. Mona Lisa (which is over-rated and underwhelming), Venus, and Winged Victory which gave me goosebumps and made me cry. We did all the “tourist” things because were tourists. Top of the Eiffel Tower, top of the Arc de Triomphe (highly recommend both), d’Orsay, dinner cruise down the Seine. Get to Sainte Chapelle in the early morning. We stood in line for an hour to get tickets, then they decided to close for lunch. We said fuck it and went to Chanel. Spent a day at Versailles and tooled around in a golf cart. The only bad meal we had (and it wasn’t bad, but we just didn’t like it) was at a duck restaurant our friends insisted we go to with them. Many restaurants are closed on Sunday.
We had a great time. How can you not have a good time in Paris???
Missed the edit window. Will you be in Paris for a full 9 days, or do the 9 days include travel days, which are essentially 2 days off your trip, making it 7 days? Either way, I wouldn’t go to London on the same trip. I love London the most of any city, and it definitely deserves its own 14 days.
I second Sainte-Chapelle, not just the stunning glass, but look at the paint details on the pillars. Every pillar is different and they all represent local plants. Fascinating.
peedin @#46: I agree that the Winged Victory of Samothrace may be the most moving piece of art in the Louvre. Every time I visit her I want to lick her all over.
But forget about the Mona Lisa and all the other tourist attractions…the joint is loaded with great art — Gericault’s “Raft of the Medusa” — and second-rate art that is extremely moving — Whoever’s “The Deluge.” Wander around and see what floats your personal boat.
An add for you: while you have time, check out some travel books on Paris about good food and places to visit, and what is available to do there in winter versus summer. Care to take in a hockey game?
Parisians are generally being dicks to everyone, including fellow Parisians. It´s nothing personal and you´re not being singled out for being a tourist.
For some it´s part of the charm, for others a real turn-off. YMWV
Mostly I go to Paris for the food. Recommendations:
Angelina, on the rue de Rivoli. The hot chocolate (‘Africain’) is mind-blowingly good if you’re a chocolate fan. Downside: you may spend the rest of the day twitching. But it’s worth it.
Bofinger, near the Place de la Bastille. The food ranges from decent to great (they do French fries [sic] fried in duck fat), but the Belle Epoque décor is beautiful, the waiters entertaining (as long as you are polite to them - ask them for recommendations of food and wine) and on the whole a nice night out. Expect late seatings, though - every time we’ve eaten there our reservation has been at 10pm.
Au Pere Louis, in the Latin Quarter. Holy crap, get the profiteroles.
I hate French cooking-stuff stores 
They assault me! I promise! I went in without meaning to buy anything! waaaaaaah Then again, I’ve bought stuff there for every kitchen my family owns, with good results… 
The big items have been covered so it depends on your interests. My lesser known recommendation is the Marmottan-Monet. The core of the collection is the art work owned by Monet - and not sold by his son. It includes some by his peers and the painting that gave the impressionist movement its name.
Some special interest thoughts:
If you are into railway history at all, you’ll be fascinated by the way you keep stumbling on odd bits of disused railway. This the Petite Ceinture:
https://en.wikipedia.org/wiki/Chemin_de_fer_de_Petite_Ceinture
If you like science museums, you’ll love the arts and metiers museum:
https://www.arts-et-metiers.net/
Do not confuse it with the City of Science and Industry, which is a quite different place. A beautiful location but the science is all dumbed-down-for-kids.
For a really quirky suggestion, one of my most fun memories of Paris is standing on the top of the Arc de Triomphe at afternoon peak hour. Because of the strange traffic rules on the Place de L’Etoile (where joining traffic has priority over traffic already in the roundbout) it’s an amazing dance show as vehicles mush themselves into an unbelievable cram of traffic.
Or maybe it’s just me.
My info is based on a few years back. The Paris Visite is marketed for tourists and you pay tourist prices. I found that buying a Navigo, marketed for residents but anyone can buy them, might be better. The monthly is by calendar month. The weekly is Mon-Sun. By careful planning when you walk and when you ride you can do better but we were happy to just buy a pass and be able to ride any time, any where.
For your 9 day stay you would need two five-day Paris Visite passes, all zones at 65.80 Euro.
The Navigo monthly for all zones is 75.20 Euro.
Yes, there is some bullshit where you can no longer buy a Carte Orange and are forced to get a (more expensive than a piece of paper) smart card.
Nope, not just you. It’s a beautifully chaotic ebb and flow.
Although you won’t be able to go in the cathedral, if you go down the street beside it there is a nice cafe where you can have lunch back of Notre Dame. 