From the artist behind the world of Cartoon Network's Adventure Time, a detail-packed coloring adventure into the deep, dark, and hidden places within our planet Expand your mind and your creativity with this wildly imaginative adult coloring book. Explore the maze of caverns, ancient insectoid temples, spooky reptilian swamps, juicy alien jungles, and forgotten cryptid cities that exist beneath our feet. You will bring these alien worlds to life as you color them in, with the pages progressing deeper underground as you go. If you're not careful, you may not find your way out again.