For me, Finnishness is all about calmness and the nature. At least in the northern parts of Finland people have a calm style of living, and they are not in a hurry (life in Helsinki can be a bit more hectic, so I’ve understood). As we have 4 seasons, we can enjoy in the nature in all of its forms.
The perfect place to combine the calmness and the nature is the Finnish mökki (cabin/cottage). Finnish cottages are usually located next to a lake at a peaceful place, where one can enjoy being in the nature. As us Finns are not that social, we like to have cottages without any neighbors. When at mökki, there’s no need to stress about anything, and you can just chill and enjoy your free-time. One of the best things is going to a rantasauna (sauna located next to the lake) and go swimming in the lake.