1. Cité des Sciences et de l'Industrie (Cité des enfants) — 19th arr. · La Villette
Hands-on science sessions for ages 2 to 6 and 5 to 10, plus the Argonaute submarine and a planetarium.
The Cité des enfants runs timed sessions of 1 hour 30 minutes for ages 2 to 6 and ages 5 to 10, per the Cité's own opening-hours page, which says online booking is strongly recommended. It lists four sessions a day Tuesday to Friday and five on weekends and school holidays. A separate Cité des bébés is listed for ages 0 to 23 months.
The Argonaute, a real submarine, can be visited every 15 minutes by booking, and the site lists it as closed every January and September. The site also lists a planetarium. The Cité is closed on Mondays, January 1, May 1 and December 25. It sits inside the Parc de la Villette, where the park's site promotes a family program called Little Villette.
Good to know: Book your Cité des enfants session before you travel, and pick the age band that matches your child.
30 Avenue Corentin Cariou, 75019 Paris, France