I was just thinking, in Disneyland there is no more room to really spread out. What if Disney could build a multi-level show-building with all kinds of different attractions inside and outside of it. What do people think of this idea?
A building that contains multiple rides would be extremely large and obstructive, and just ugly IMO. But if they were to build rides underground, like HM and POTC, I'm sure it would work just fine - they would just have to find the appropriate area to build it. I can only think of 1-2 places they can build larger-scale rides at the moment.
I don't think we have to worry about going underground or building skyscraper attractions until we replace some of the less "appealing" attractions and start using up all the flat land that still exists (of which there is still plenty).
Still, Disney should also return to their creative ways of building small profile multi-story attractions... POTC, HM, Splash Mountain, etc.
There are many unused areas Disney can use to expand. However, they need to majorly fix Tomorrowland before even considering any expansion. I really believe Tomorrowland needs to be fixed before Frontierland gets an expansion. ToonTown, too. Then Frontierland can get work done. Once ALL lands are up to Disney standards, THEN expansions can happen at Disneyland. Until then, it just seems like a waste of funds. That's my opinion.
I think the one land that would really believably work as a multi-level experience would be Tomorrowland, and even then, the layering of attractions could only be minor at best. I've seen concepts for multiple attractions going through the same space (Indiana Jones concept art comes to mind), but other than the idea of it all going through the same scene, I can't imagine the amount of engineering issues that might come if show buildings were actually stacked. :S It's an interesting idea either way though, and perhaps in the distant future? : )