Why isn't it "Göteborgs hamnen"?
After a word in genitive, we can't have the determinate form. It's the same in English, really. You don't say 'the man's the book' either.
I didn't realize it, I'm not a native speaker :). Tack!
I put that as well because of the rule I thought I remembered right: that possessives become definite. Is this different because it is a genitive, or is it because it is the possession of a non-person?
The rule is the opposite - possessed things are inherently grammatically indefinite.
Does it HAVE to be "Göteborgs hamn"? Is there no room for variation? You really can´t say "hamnen av Götenborg" or something like that?
No, Swedish generally doesn’t use that of-construction.
Okay. Fair enough.
You can say "hamnen i Göteborg" but that is not really the same meaning ("the port in Gothenburg").
Isnt "finns vid" acceptable instead of "ligger i"?
No. It sounds unnatural.