Hmm no one knows for sure, but we can do a fair amount of guesswork here, by the look of their uniform, it's obvious that it's somewhere cold, the quidditch team is from Bulgaria, so obviously, Krum lives somewhere there, remember, that Krum's wand was made by Gregorovitch? The wandmaker who claimed to have owned the wand of destiny? When Voldemort went looking for him, he went to a house where people were speaking in German- they didn't know English. So it's clear that Viktor is from Bulgaria. Now Durmstrang by the looks of it is probably somewhere in the north of Norway or maybe Sweden.
