There might be spoilers here, but then again … I have no idea what this place is about. Doesn’t make much sense to me. It is a place west of Norrmyra Artillery Base towards Nilssons Marinebygg, and the picture below is taken from the radio mast at the nothern point of the penninsula.
Obviously I ran there and couldn’t quite figure out what purpose it serves. Go to -3080,-3080 if you haven’t been there already, and would like to find out more. I think it is pretty well hidden.