Let me attempt to clear this one up to the best of my ability...
At the time of its inception, Eisner asked for plans to a new E-Ticket attraction to go into the Magic Kingdom. Two teams of Imagineers were formed, each creating a new "mountain" to go into the same location. One team created what we have come to know as Fire Mountain. This attraction would be based around and inside of a volcano. The story details never really got out beyond the eruption scene, but most of us who have been given the story and concept art can tell you that many aspects of Fire Mountain made their way over into Tokyo DisneySeas' Journey to the Center of the Earth.
Now, I didn't forget the other team, just had to give some background on the main attraction there... The other team created what came to be known as Bald Mountain or Villain Mountain in its later years. Bald Mountain would be a flume ride, just like Splash Mountain but with a more sinister story. The main sequence of the attraction (the equivalent to Fire Mountain's eruption) was where you as the rider floated into the Disney villains' meeting location, alarming them and send you down off the side of Bald Mountain's "waterfall." I never saw any concept renderings though the description featured the chernabog (from Fantasia) lunging at you just before you took the plunge (much like the dinosaur coming out at you at the end of Dinosaur).
Both ideas were meant to go in the Fantasyland area on the 20,00 Leagues plot. Well, Eisner never really decided on a winner between the two ideas due to a massive budgeting problem caused by EuroDisney's recent monetary shortcomings. The ideas were shelved, but many of their aspects have been adapted for use in future Disney attractions.
And may I just add in that neither of these two attractions were ever planned for Animal Kingdom, Beastly Kindgom or such. One of these attractions has been taken off the shelf several times and expanded (conceptually) for further but so far non-tangible use...