>>719248156
Depends on what you're looking for, but I wouldn't advice staying inside circle 3 (pic related) and especially staying away from Helsinki unless you just want to see a bunch of immigrants and woke stuff, might be cool for a quick visit for some of the architecture but I wouldn't center my whole trip around the places.
Most of the cities here are really small but I'd probably recommend Tampere or Turku, Turku moreso if you're interested in seeing some older city areas and whatnot, Tampere has a pretty cool museum with an extensive vidya section and an active nightlife.
Jyväskylä is also pretty cool, but it's quite far away from everything else, it's a student city so mostly younger people live there, not a lot to do though, especially if you don't have a car.
The charm of the country really comes from the smaller towns which there are too many to mention and the lakes, woods and whatnot attached to them, but if that's not your jam the cities I already mentioned might be more your speed.
Best time to visit is obviously going to be during the summer, winters here are more or less torture and we take it out on everyone, people get real pissy and anti-social.