Take the Batobus ticket …
This covers from Jardin des Plantes to the Eifel tower …. (plus more)
Jardin des Plantes isn’t that spectacular s a zoo but just around the corner on Rue Monge is a Roman Amphitheatre .. you can also take Institut du Monde Arab and the Mosque rest/garden (which is not what you might expect) … but a decent place to stop for a mint tea …. (there is even a Hamman attached but you won’t have time for that and it’s segregated male/female) – (Other than that it’s really not what you might expect from Mosques in the UK)
If you ignore that then you can wander from there up to the Pantheon and then wander down Rue Moufftard (At the top of St Geof de Hillaire, almost next to the Church and Bombadier pub) is a rest L’Ecurie (stables) .. it only serves Steak and chips if its still open….
Wander down Moufftard..for some trendy shops (probably a street market and maybe dancing in the square at the bottom . and end up back where you can take the batobus…
Or if you don’t go down Moufftard instead you could just wander down Rue St. Michel to Notre Dame
(where again you can pick up the Batobus)
Everywhere is walkable … so you can even walk from Notre Dame to Pigale for sample… via the Grnds Boulevards etc. but I prefer missing that area and also Champs Elysees out… (I lived there for 7 yrs)