What to do with an 8-hour layover?

Frankly if it were me I wouldn’t risk it. By the time you would get out of the airport and into the city, and then allowing for time to return to the airport arriving 3 hours before your flight, it’s probably not worth the trouble. Maybe consider a small town closer to the airport?

I'm with Andrea—I wouldn't risk it either. I had a 7 1/2 hour layover at CDG a few years ago, and opted to stay at the airport (and that was without a transfer from ORY). See if you can buy a pass to one of the many Air France lounges. Some of them are very nice.

Agree with Andrea and Mardee. Just not worth the stress factor. Had rather possibly be bored at the airport than stressed out about getting back on time. Perhaps a good meal at one of the nicer restaurants will use up some of the time.

What month is your travel ?

Will you have checked bags?

If you estimate say 90 minutes for getting out of Orly and making it to CDG (which may be optimistic), plus the need to be at CDG three hours prior to a flight to the US, that is four and a half hours of your eight hours used up, leaving you with three and a half hours.

If you go somewhere else, I guess you get back some of the time it would have taken to get to CDG, but then you will still need to get to CDG

So you have about three hours to "play" with, if your flight from La Réunion arrives on time, and there aren't any horrible transit issues that day.

You could go visit the chateau at Chantilly, I guess.

get a day pass for a club or a day room at the Sheraton or Hilton

Thanks Everyone. I will follow your advice and go directly from ORY to CDG.

Part of me was hoping there was a Metro stop one or two stations away from the airport where we might stop for a bite. I know airports have food, but we were looking for just one more experience before heading home.

I disagree with the others. If you take the RER B, you'll be going right underneath Paris. If you get out of the RER at Gare du Nord, you will find lockers inside the Gare to store your luggage. You should have time to walk to the top of Montmartre which is just north of the station.
Then come back down, get your luggage, get back into the RER B and go to CDG.
Leave an hour from Orly to Paris, an hour from Gare du Nord to CDG, and 3 hours before check-in. That leaves you 2-3 hours in Paris.

Thanks for your reply, Bets. I think we will have at least 90 minutes to play with. We will have visited Montmartre earlier in May, so I was thinking about finding a quick lunch somewhere a metro stop or two away from CDG. Can I jump on a metro at the RER B near CDG and find something like that? Thanks!

No, there’s nothing in the area around the RER/CDG airport. You would need to stop along the RER B in Paris if you wanted to do this. (E.g. you could get off at St Michel and find a way to stash your luggage with NannyBag or Stasher or whatever, or you could do the same at Luxembourg RER B stop for the Jardin de Luxembourg are.)

But no, there is nowhere nice near CDG airport accessible by RER B.

So here’s my suggestion

Take the Orly bus to Denfert-Rochereau. There’s a market street (Rue Dagaurre) just around the block. Have a nice meal, do some people watching. Then walk back to the Denfert Rochereau station and catch the RER b straight to CDG.

Rue Daguerre is a nice little street complete with all kinds of nice options for eating.

The Orly bus to Denfert-Rochereau looks like a winner! According to the airport website, the Orly bus departs every 10 to 15 minutes and arrives at Denfert-Rochereau half an hour later. We can grab a quick lunch in the area. The RER B will get us to CDG within approximately 45 minutes. If I'm doing my math correctly, that's an hour and 15 minute trip time to CDG. By contrast, if we take the train directly from ORY to CDG, it will take a minimum of 85 minutes up to as much as 100 minutes.

I was just in that area this afternoon. It is not the height of tourist central but there are some really nice cafés, restaurants and you’re in a real Paris community where people live. If you have tourism time, the outstanding resistance museum is very close but with luggage, that might be a bit much.

I have taken both that bus and the RER and I would tell you that it’s an easy transfer. Assuming it’s working, there is an elevator down to the RER line so you don’t have to go down the stairs to your catch the train. Now of course in Paris, is in a lot of Europe, assuming the elevators are working can be problematic, but let’s think positive.

There are several hotels in CDG. You could rent a room to relax before the long flight home.