The way home required a overnight stay in Helsinki.
The airport has a good connection to the city. 24 hours
bus ticket is a good option. Free wi-fii at and lockers for baggage can be found at the airport. A lot of people spend a night there waiting for another flight. I managed to visit Helsinki both in the evening and the next day in the morning as my plane was in the afternoon and I had the 24 hours ticket. The city has a lot of old buildings. I visited Suomenlinna Island too where is an old fort.