On a recent visit to Disneyland I spent time taking in the latest exhibit in the Disney Gallery, Mechanical Kingdoms.
The exhibit's subtitle is "Steam-Driven Visions of a Victorian Future," and it features some of Disney's many "retro-futuristic" designs.
The exhibit particularly emphasizes designs for Disneyland Paris, which has Discoveryland rather than Tomorrowland; Discoveryland's concept is that visitors experience what "visionaries" of the 19th century dreamed of the future. There's a heavy Jules Verne theme including a walk-through of the Nautilus from 20,000 LEAGUES UNDER THE SEA.
Some of my 2009 photos of Discoveryland can be seen in this post.
Here's a 1987 design of the Disneyland Paris Space Mountain by Tim Delaney:
The Disneyland Paris Space Mountain is much more intense than the Disneyland version, incidentally! I'm pretty sure I was upside-down at one point, but it was dark (grin).
One of the Disneyland attractions which fascinated me most when I was young was Monsanto's Adventure Through Inner Space. I think I was pretty convinced at one point that people really shrunk entering the ride!
Here's Herb Ryman's 1966 design of the first part of the ride:
The Discovery Bay concept created by Tony Baxter in 1974 never became reality:
Here's a 1979 Marc Davis design of an "iron horse" for Epcot:
There are many additional photographs of the exhibit at MiceChat and Disneyland Live.
Previous Disney Gallery exhibits: Magic on the Water, The Colors of Mary Blair, Trains of Disney, Crowning Achievements, and Tiki, Tiki, Tiki Realms.