16 birthday with grandson in Paris

What is he interested in?
Food tour or a pastry tour?
How about the Catacombs?
River cruise?
Segway tour?
Soccer stadium tour? https://stadiumtour.psg.fr/en/

We took our daughter to the Effiel Tower for a birthday dinner. We ate at the restaurant on the second level, not the super expensive one further up. I had found a chocolate Effiel Tower so I had that placed on her plate. She enjoyed it very much.

What time of year is your grandson’s 16th birthday? Angelina Paris is famous for their thick hot chocolate: https://angelinaparisusa.com/.

I'll bet most teenagers would love Eternelle Notre Dame. It's a virtual reality experience that shows the building of ND, starting in medieval times and ending at the fire in 2019. It's just in front of Notre Dame, underneath the parvis. It takes about an hour. Make sure, if you buy tickets, you buy them for that location, as there's one at La Défense as well.

Right. I'd ask the young man what might trip his trigger. In the meantime, you might look at some activities that may hold particular appeal to active teenagers such as....

Paradox Museum:
https://paradoxmuseumparis.com/en/

Street Art tour:
https://www.myurbanexperience.com/en/98-street-art-private-tour#desc_bottom

Immersive digital art (this looks like a lot of fun!)
https://www.atelier-lumieres.com/en

Links to that virtual reality experience at Notre Dame suggested above:
https://www.eternellenotredame.com/en/experience
https://eternellenotredame.placeminute.com/event/musuem/eternelle-notre-dame-une-expedition-immersive-en-realite-virtuelle-sur-le-parvis-de-notre-dame,39035.html?date=0&_locale=en&

Thank to everyone the responded. Great ideas

If he has any interest in airplanes take him to the National Musee d' Air at La Bourget airfield north of Paris. World class, and the three classes of French teenagers that were there when I visited seemed to be having a very good time.

Fat Tire Bike Tours. My son and 10-year old granddaughter did one and loved it.

Josephine Chez Dumonet has an amazing Grand Marnier Souffle and if you tell them it is his birthday they put an impressive sparkle cone on it; the people at the next table on our recent trip had one.

I second Eternelle Notre Dame -- amazing and I think particularly memorable for a young man.

Does the lad like football (soccer)? My 15 year old daughter and I had a great time at a match in March. Crowd is electric. You see some French culture. Lots of fun!

Not sure when you’ll be there but if during the season and the lad likes sports, this could be fun.

My daughter is 15 and is really interested in art museums and Napoleon. So it really depends on him. She picked Paris because of the Louvre. But we're also eager for the Army Museum, among other places.