Location of Durmstrang

I was reading GoF when I was wondering where Durmstrang was. Krum was obviously Bulgarian, at least on one side of the family, but he couldn't be living in Bulgaria, since it isn't up north enough to fit the few descriptions we have, especially about the winters. So maybe Krum lives up further north, like several muggle sport players do when it comes to World Cups, the don't have to live in the country to be on the team, they just have to have the citizenship.
So, where about do you think the Durmstrang Institute is?

I'm not sure, I was just thinking of that today because my best friend showed me a detailed map that she made of Durmstrang. (Which is totally awesome!!!)