In the 1st Journey into Imagination incarnation, the Realms of Imagination are five different locations created and visited by Dreamfinder and Figment. The realms are Art, Literature, Theater, Science, and Film respectively.
How each realm look like and how they're created
Art
The Art room was mostly white colored, and had a large painting Dreamfinder was making using a large fiber optic paint brush, a carousel with giant carousel animals, and a pot of rainbows held by Figment. This Artistic realm is created from a rainbow amongst other art objects.
Literature
The Literature room was mostly focused on suspenseful tales and had Dreamfinder playing a massive organ with words coming out of it, words that turned into their meanings, a massive book featuring the raven from Edgar Allan Poe’s poem cawing menacingly, and books of horrible monsters Figment tried to keep closed. This spooky story of a realm is created from "Ghostly Shivers" and other horrifying ideas.
Theater
The Performing Arts had Figment trying on costumes backstage while Dreamfinder conducted a laser light show in the manner of an orchestra conductor. According to One Little Spark, the realm of performance is created with such ideas as "some happy songs, some snappy dances, costumes and sets, spoof and romances" which ignites "a brand new show."
Science
The last of the rooms, the room that housed Science, featured a large machine that Dreamfinder was operating that took a closer look at the workings of nature such as the growth of plants, the formation of crystals from minerals and looking into space. The realm of technology is made out of scientific ideas such as "electron beams and crystal prisms."
Film
As the rider's pictures are taken, they see Figment surrounded by several movie screens of him being a scientist, a mountain climber, a pirate, a superhero, a tap dancer, a ship captain, a cowboy, and an athlete. This is probably from leftover theatre ideas.