>>116306I can't say which one is best since I've only been to Hardangervidda, but that's a place any nature freak must experience once in their life. As a bonus, it's also where the Hoth scenes from Empire Strikes Back were filmed.
However, there is no midnight sun there. The best time to go there is in July and then the sun is down for about 6 hours every night, but it doesn't get entirely dark.
Also, keep in mind that it can get cold even in the summer. Snowfall is rare, but possible.
