This chapter focuses on “imaginary space” – literary spaces without a real-world referent. The question of how detached fantasy worlds like C. S. Lewis’ Narnia came to be thinkable in the twentieth century frames the chapter, which argues for fantasy space as a strategic response to the alienations produced by twentieth-century capitalism. Weaving together a history of exploration with a history of different types of imaginary space, the chapter traces the emergence of works like Lewis’ The Chronicles of Narnia out of earlier forms of imaginary space. Types of space reviewed include the settings of the traveler’s tale (e.g., Jonathan Swift’s Gulliver’s Travels and Wu Cheng’en’s Journey to the West), Thomas More’s Utopia, and the Romantic atopias of Mary Shelley’s Frankenstein and William Wordsworth’s Prelude. The chapter draws on the theories of Yi-Fu Tuan, Fredric Jameson, Henri LeFebvre, and Michel Foucault to explain the distinctions between different formations of imaginary space. It concludes with a reading of Susanna Clarke’s Piranesi as a text reflecting the changing value of fantasy space in the twenty-first century.