Why the Kirjasto 10 called 10?
Library 10 is located at Postitalo, which used to be the main post office of Helsinki. The building is not anymore owned by Posti but it still contains a post office on its ground floor. The post office has been commonly known as "Helsinki 10" because the postal code for city center of Helsinki is 00100. Library 10 is located on upper floor of "Helsinki 10". That’s why the name "Library 10" was chosen.
It's also open until 10pm most days of the week!