Paris in 9 hours?

It may be doable to go to one but definitely not both. The airport is a 35 minute train ride outside the city plus you have to store your bags and get back early enough for your next flight. I'd pick the Eiffel Tower. :)

And you may just have time to LOOK at the Eiffel Tower -- but it's pretty impressive just walking around the base even if you can't wait in line for the ascent. Look at the Seine. Eat a crepe.

What time does your flight pull up to the gate?
What time does your flight for Italy depart?

We fly in at 8:15am and fly out 5:30pm. We both have global entry so customs should be fast for us.

Monica, Unless things have changed, Global Entry doesn't mean diddly when entering France. All it does is speed up reentry into the U.S. and gets you into the TSA "precheck" screening line within the U.S. Someone please correct me if things have changed. TC

To separate the 2, Immigration (Passport check) will happen regardless. There will be separate lines for EU residents and all other passports. Global entry means nothing. Customs is pretty much walking out the door marked "nothing to declare". I assume your luggage will be checked through to Italy. You will also be in possession of a boarding pass for your connection. So you stand a good chance of standing in central Paris by 10 am. Plan on heading back to the airport around 2:30 so you are back at the airport by 4, all you need to do is get through security and walk to the gate. If the weather is rotten, you may wish to go to the Louvre. You don't even need to go outside to get to the museum on the Metro. If the weather is nice, maybe the Eiffel Tower and some strolling about Paris.

I'd say you have time for a few hours in Paris. I'd allow an hour each way to and from the airport. I'd use the RER "B" train but you could spring for a taxi if you want to see more and don't mind paying, say, 50 euros instead of 20 each way (assuming there are two of you, if more then the RER gets more expensive). If the weather's good, and May is a good bet, I'd stay outside and walk along the river (welcome relief from economy class). Get off the RER at St-Michel, look back at Notre Dame, then walk west past the Louvre (across the river), on till you see the Eiffel Tower on your left, maybe you'll have time for a 90-minute boat ride leaving from either the ET or Pont Neuf. Have a nice lunch somewhere. Don't try to go up the tower or into the Louvre, they'll take too long. Then head back in plenty of time for airport security and such, leave a healthy margin.

Global Entry and Pre-Check are nice US amenities that won't do anything for you elsewhere. But they'll help at the US ends of your trip.

Thank you so much for the tips and recommendations!