Sea Castle, as first envisioned in Epcot's Horizons, is a futuristic, floating city of tomorrow. The basic idea is, you take everything that is Autopia, MBC, and the Subs, and tear them all out to build afresh.Originally Posted by dsnyfnatic
The Subs have a brand new, built from scratch, showbuilding that takes you beneath the city to view new types of underwater technologies. The Aquatopia would take you on a sea-level tour of the model city. Autopia would provide a view of a smart freeway of the future, etc. Basically, you create a multi-level view of Progress City or something along those lines.
One of the simple tricks to keep this as a transition land between Fantasyland and Tomorrowland would be to use the Aquatopia waterway as a sort of moat around the floating city. Instead of the old MBC boarding area, you board where Fantasyland Autopia used to board. From the shore, you have landscaping and rockwork that mirrors Matterhorn and the rocks around the current Sub Lagoon. As you pass along the Tomorrowland side of Matterhorn, you still mostly see a natural setting with trees and such. It's only as you get closer to the loading area that you see the tall spires of the model city.
One of the other ideas I've been tinkering with is to have a second PeopleMover station within the model city, so that like a real city of the future, you get to the model city's Downtown by Tomorrowland transportation. But that's just one possibility.