Attitudes vary from person to person, but I don't really think being 20 minutes from nature really counts. I lived in Paris until recently and had a really rough time for a few reasons, but the biggest one is was the lack of green places to walk. Whenever I brought it up to anyone, people would say "oh, what about Bois de Boulogne or Bois de Vincennes?" Both were inaccessible by foot from where I lived due to distance and would take 30 minutes to get to by public transit. So what's the idea, then? We should budget an hour in a subway tunnel each day so we can spend some time in a park? That's no way to live; nature isn't something we should treat like a museum. It is something we should feel a part of.

For me, thankfully, there was an easy solution: I moved to one of the towns just outside of the city. Now I have ample access to lots of trees, birds, flowers, etc. If I get on my bike, which I do frequently, I can be in some really beautiful regional parks within 40 minutes or so, and the ride there ain't too bad either.

I love Paris and would love to hear about some good Paris-adjacent nature opportunities if you're up for sharing.

My favorite place to bike is Parc naturel régional de la Haute Vallée de Chevreuse (French people aren't into the whole brevity thing). I can't speak to hiking but I have to assume there are nice walks to be had in the area because I frequently see people with hiking gear on. You can get there from Paris on the RER B: just take it all the way south to Saint-Rémy-lès-Chevreuse. Île-de-France is, by and large, quite flat, but Chevreuse is a nice valley so you can get some really pretty scenery.

EDIT: I'll add that last fall I was biking around there with my wife and we found some most righteous porcini mushrooms growing on the side of the road. It really is nice out there.

I should also add that nearer Paris is Forêt domaniale de Meudon, which is in the direction of Versailles. Nice forested area. I can't speak to the walking/hiking but I assume it is not bad (I've only been out that way on bike).

I'm a big proponent of walkable cities too, but I diverge from these people in that I don't think it's desirable to make everyone live in a dense urban environment or else extend public transit to every corner of the US in the name of abolishing cars.

Nature is also against walkability when it puts frigging hills on my way! Also the weather is way too agressive near the equator... I can endure it with sports clothes but not before work.

Seriously: walking/cycling on Amsterdam, Lisbon or Paris when the weather is 15 °C, mostly on flat ways, is a pleasure. You arrive at the office just a little heated up, I imagine.

That’s just excuses though, people cycle even in Norway where it’s below freezing most of the year

I find it much easier to do exercise in the cold than in the heat. In the cold it's just a matter of having the right gear and layers. In the heat, there's nothing you can do. It'll be extremely hot, you'll be sweating like crazy and get tired quicker (or at least I do).

Well... exercising in the cold makes you hotter, that makes sense. And I bet they have Canada-level of socks/parkas/etc which you can remove as you get hotter.

I'm okay with being the "weak person" who doesn't enjoy cycling in below-freezing weather.

Walking hills is the best walk.