When I am asked of typical aspects of Finland and Finnishness, the first things that come to my mind are sauna and nature.
Sauna is likely the best known part of Finnish culture around the world. There is no better place to relax after a strenuous day or to warm up on a cold winter day than a 100° hot sauna. Whereas a sauna is considered as a luxury in most countries, it is completely normal in Finland, which is proven by the fact that there are about 2 million saunas in Finland, even though Finland only has a population of 5.3 million. Most houses/apartments are equipped with a sauna which is pretty unique when comparing that to other European countries. In my opinion the best sauna experience is staying in a summer cottage by a lake, when you can mix sauna sessions with an occasional round of swimming in the lake.
Finnish nature is unique and known for its forests and lakes. Around 78% of the land is covered by forest and around 10% by lakes and other waters. So regardless of where in Finland you live, the distance to lakes and especially to a forest is usually very short. Also, the mix of forests and lakes makes the Finnish landscape a beautiful one. It’s amazing! Especially when you’re standing by a lake (e.g. Saimaa), you will usually have a great view over the lake and the adjacent forests.