Almost every attraction and pavilion at EPCOT has some sort of hidden room or lounge. Most of these were created as private entertainment spaces for the original corporate sponsors of the attraction. As Disney has moved away from the corporate sponsorship model, probably not by choice, these lounges have fallen into some of the folklore and mystery that sounds the park.
The lounge in the former “Wonders of Life” pavilion even made it into Ridley Pearson’s Kingdom Keepers series as the “Mary Poppin’s Room.” The room does have a big carousel mural, which is evocative of that scene from the movie, but it’s traditionally known as the Carousel Room.
I’ve been in that room before, but wasn’t allowed to take photos due to the nature of the meeting. Zannaland, on the other hand, encountered no such restrictions. She just posted some great photos of the secret lounge including the carousel murals. Go check them out if you want to see something most guests don’t even know exists.