I was under the impression that the promised land was the Northern Crater, something in the game gave me that impression though I cant remember what it was. Maybe something to do with when Sephiroth fell into the lifestream at Nibleheim, he followed the paths of the stream till he wound up at the promised land in the crater.

This could just have been HIS promised land as it was where he could gather enough energy to summon Meteor. (that would kinda make it consistent with what others say about each individuals promised land)