there are a lot of outdoors stuff 1-3 hours outside of NYC. NYC itself does have a lot of parks too, of which Central Park is the largest example.
You can see quite a bit more like the Adirondacks you're willing to drive 5-6 hours, but a drive like that isn't suitable for a day hike.
You can also find some smaller trails and untended areas on the outskirts of the city (eg, Marine Park in southeast Brooklyn). But these tend to be.. well small.
Anyway my point is, like most big cities, it's difficult to really get "outdoors" with any measure of convenience.
The most well known maybe, but not the largest. Pelham Bay Park in the Bronx is more than 3x the size of Central Park