"...vaguely located in the Outer Ocean..."

Yep, it's all very vague. In English 'vaguely' can mean 'just about', as in vaguely remembered 'just remembered'. I think we might need to back to the original Greek to find out what they meant by 'vaguely' - it could mean an island 'just barely' glimpsed from France for example?

Much as I respect the Inuit's, I cant really see them as being the inspiration for an ancient Greek interest in a mythical island inhabited by a people they called the Hyperboreans; but who knows - it's all way beyond me. I've just got this gut feeling that knowledge of the megalithic structures of these islands, and the people that constructed them, travelled far further than we imagine or give credit for; but again, who knows...