Marsvin means guinea pig in Swedish but that's not what this castle is about as it also means harbour porpoise in Danish and this used to be a Danish province. Marsvin was the name of a very wealthy Danish noble family. The castle outside Ystad has a lovely rural setting and romantic turrets and towers. It hosts equestrian shows and concerts but is also open for visitors who wants to see it.
This was the location of Wallander's home in the books by Henning Mankell - although the number was never stated, I understand the description matches this apartment block.