Heretic 2 had this fucking map as loading screen that teased a lot of stuff but then the path taken was just a straight line from Silverspring to the Cloud Fortress.
Why the fuck would you mention utterly specific shit like forgotten cities of ice or harpy islands and not follow through with them?!
There was also a giant globe in one of the earlier levels located in an elaborate room that seemed to originally have been a "find and enter the right combination of constellations and seasons" puzzle (Corvus even comments on this when you enter the room) but in the final game you just flip two switches and the "puzzle" solves itself.