when i was living in japan i lived in aomori which is the most northern prefecture in the main island. There they speak two dialects which are simular to each other but extremely different from standard japanese. The left part of the prefectue speak tsugaru-ben and the east part of the prefect speak nambu-ben.
when these people speak outside there area (for example tokyo) people often think they are speaking english or some other language because they do not understand a word they are saying. apparently these dialects are the hardest to learn.
not only is the internation different but the words are also different.
for example if you want to say where are you going "doko ni iku no?"
it will sound like "do sa igu no?" (most of the time they just say "do sa")
and if you are going to the public bath you would answer "onsen e" or "onsen ni" but in this dialect you would say "yu sa"
its a very difficult dialect but fun to learn