I've been there once and it had nice saunas and the possibility to go for a swim in between. Website says that the swimming spot should be open throughout the year, although with a weather reservation.
Take a dip in the Baltic and do other spa things at Löyly? Do a one day or overnight trip to Tallinn in Estonia by ferry? Have a hot chocolate in a little hut (or outside it with the locals, if you’re into that) at Regatta?
If you are a public transport nerd you should definitely try the brand new lightrail tram, it takes about an hour from Keilaniemi to Itäkeskus (or the other way) and shows you some less central parts of town.
As a librarian, I must of course also say that our libraries are cool. The one I work in is the first library to be planned and built for public use, in service since 1882 www.helmet.fi/en-US/Librar...
If you are into art, then the Diedrichsen museum is a personal favourite based on a private collection, located in a very nice part of town www.didrichsenmuseum.fi?lang=en
The MIG on top of Verkkokauppa. Take the train to Hämeenlinna or Tampere. The Design Museum. Didrichsen Museum. Walk on ice if it’s solid enough. Rent skis at Paloheinä
The airplane museum in Vantaa is nice, in case you wondered who had swastikas painted on the wings first. The museum's senior guide doesn't like to accept the negative impact of air travel on our livelihood, though. Do feel free to teach him. 😉
Oooh, nice! I stayed there for a month and a half a while ago, I've seen most parts of it. In a better season though 😅
Lauttasaari is probably my favorite part, the whole seaside park area along the south/south-west side, I've spent many evenings there :) 🌅
You can also go through a chain of islands from Ruoholahti via Lauttasaari and north from there and come out in the north of the city, on a bike, but probably too cold for that now… The park on the south-east edge of the city (Kaivopuisto) is pretty nice too. And the Töölönlahti neighborhood too.
I liked Suomenlinna, but I don't know if that's open now. And I've eaten some good things at the Elite restaurant at Hesperiankatu (it looks very fancy at first sight, but I didn't feel bad there dressed not-fancy ;). Lohikeitto is always worth trying, not only there (it's not hard to find) 🐟
Thank you for the recommendations! yeah, that side of the city is lovely. I’ve been walking to Seurasaari and around that area a few times now. That restaurant looks very nice
Suomenlinna is a regular part of the city where people live, so it's always open. If the Suomenlinna Toy Museum Café is open, that is well worth visiting.