Helsingin Kaupunginmuseo is a free museum our tour guide suggested and enjoyed it because they had…read moreclean restrooms, nice seating, and it felt very calm and wasn't crowded.
The museum would probably be three stars if they tried to charge for it as the exhibitions are a bit of a let down and don't feel all that engaging, but some of the historical furniture was interesting as was the fridge with historical "food".
All in all, if you're in Helsinki and have some time to waste I'd recommend it, but generally keep your expectations low.