I travel a fair bit within Norway, mostly due to work, and up North you're almost guaranteed to see them if it's a clear winter's night. But the sighting that made the most impression on me was here in Oslo. I was out skiing alone one evening and wasn't expecting to see anything as it's not that common this far south - and was treated to a fantastic display over the entire sky, complete with a "red crown", one of the rarest. Very beautiful, and awe-inspiring :-)