I suspect that the “story” of a tour through Disneyland was, roughly, originally intended to be a clockwise tour from the ancient — in Adventureland — through time, toward the future of Tomorrowland.  

Which is one of the reasons that trying to change the “future” into the Jules Verne era worked so poorly.  

And why the Adventureland tour remains so successful, because it is a multi-layered introduction to time travel, as it is more a nostalgic-look-at-the-ancient than actually being engulfed within the mists of time (I suppose to keep it within the “America Rules!” sense of the entire park).  

And these transitions, which are discussed so ably in that post, are part of that (literally) wonderful trip through time.