From LostEpcot:
"The Odyssey opened with the rest of the park in 1982 as a restaurant and complex. Technically part of Future World, it sits in the transition zone between Future World and World Showcase (between Test Track and Mexico).
The restaurant served hot dogs, hamburgers, and salads for lunch, and beef stew, fried clams, and sweet and sour chicken for dinner. During the late 80s and early 90s, there was also a live show with characters to entertain guests at the restaurant called "Mickey's Rockin' Celebration." The Odyssey also housed first aid, baby services, and lost children.
In July 1994, the Odyssey Restaurant closed, with the building only to be used for special events (the restrooms and services can still be used by everyday guests, though). Currently, the Odyssey is listed as the "Odyssey Center" on the Epcot guide map."
Its basically used for group events like cheer leading competitions, high school bands etc...
I too wish it could be refurbished and reopened to guests.