I live in Helsinki, and I visit Linnanmäki amusment park (swedish: Borgbacken) every year with my family and friends. It's really something awesome! I recommend it definitely to families with children and teens, but also adults can have a whole lot of fun there! There are plenty of different machines and roller coasters. Linnanmäki is the greatest amusmentpark in the Nordic countries, when you look at the amount of rides!
The park was founded 1950. The prices are pretty high, but don't worry, the entry is free (unlike other amusment parks in the world) and a big part of the money they get, are going straight to an organisation which is supporting and working for the children's best in Finland.
If you visit Linnanmäki, I really recommend you to eat "Softis" (soft ice) and "Hattara"! It's lovely! And one thing about my pictures, don't belive those attractions are the only ones, I don't just have pictures from others.
I hope you can visit the park, and have fun!More