What is the difference between "i centrum" and "på stan?"
When you go downtown you say "på stan" (direction city centre) and when you or something is downtown you say "i centrum" (in the city centre).
How unnatural does Banken är i centrum sound?
Not all that much, but it's still better to use ligger.
What about "Banken finns i centrum"?
could you say banken ligger icentrum also?
No, the writing together only applies with a handful of time adverbs.
Could one say "Banken ligger mitt i stan"?
I don't think so. I think "mitt i stan" is a much smaller area than "downtown".
doesnt this actually translate as Banken ar centrum
No. Downtown means "i centrum".
Banken är centrum
"The bank is centre"?! No, that's incorrect. "The bank is in the centre" = "The bank is downtown".