I really, really like
Seurasaari in Helsinki.
Google Maps
It's not particularly big, but it's very wooded, overrun with precocious red squirrels (who'd mug you for a nut if they could only work out how to use knives and wear leather jackets, i think) has a fun little
museum in there and is just, generally, a really nice place to walk around and relax in.
I think the bridge over a little watery expanse to get onto the island kinda mentally prepares you for the division of park from city, makes it a little more special.
Oh yeah... I forgot the nudist beach... haha!
Nordic types. Love it.