(Finnish Baseball; also informally known as "pesis")
The national game of Finland.
Pesäpallo was designed by Lauri "Tahko" Pihkala in 1910s.
The roots of the game are in old Finnish ball games, most importantly a game called "kuningaspallo" ("king ball") that was popular back then. Apart of that, Pesäpallo draws ideas heavily from American Baseball.
The game has been on some wane during the period after the wars, but it still goes on and people are still heavily reviving and pushing it. (Well, personally, as long as the kids in schools are made to play it it survives =)
The basic idea of the game is simple: One player of the team hits the ball with a bat and runs through the three bases, while the other team tries to catch the ball and return it to home base.
The largest differences between Baseball and Pesäpallo are the shape of the playing field (much narrower), and the vertical pitching.
The town with most baseball fans and playing activity is Sotkamo.
The official international rules (in English) can be seen at <URL:http://pesisnetti.pesis.fi/755>.
Sources:
http://www.students.tut.fi/~amv/hypmed/historia.html
http://pesisnetti.pesis.fi/17