I really think we need to hybrid these two ideas together. The mountain, and atlantis.
This is how I see it.
The Entrance would be atlantis, a town street that leads to a temple standing atop a magnificent mountain. Domed ceiling, large towers, archways, statues, all adorn this temple. A stair in the middle of it leads up to a ride.. (If weirdone would like to elaborate on the Temple in the sky attraction, maybe it would fit here..) On either side of this stair would be access to under the mountain, which would be a large 'couryard' the hub of the park, large pillars would appear tio be holding the mountain up, as waterfalls fall, crystals sparkle, etc. Here there would be gates to the different lands.
Now, lets step back. The road that atlantis would be on would be shaped like a lower case 't' with the mountain on the top of the t, and two, lesser attractions on the cross line. The rest of the building would be your regular shops and resteraunts, customer service, stroller rental, etc. Soooooooo...Concept art? Anyone?
Just some quick sketches? I'm gonna give it a whirl, but I'm heading to disney tommorow for a 3-day vacation, so I won't be getting back with you for awhile...
Also, throw some Ideas out for the two lesser rides...Maybe on featuring the movie atlantis?