This volume explores a dimension of reality usually scoffed at by rational-thinking individuals living in modern industrialized societies, but still experienced by these same individuals when they are in a stage of sleep known as rapid eye movement (REM) sleep; this is the stage in which vivid and bizarre dreams are a person’s living reality. While in this stage, we believe what we experience is real, but then deny its reality upon awakening as we go about our daily routines. Yet, in many cases, a dream with vivid imagery and bizarre goings on is communicating with the dreamer in an archaic language directly associated with an “Otherworld” reality. This reality exists within us and expresses concepts and ideas about our realm of existence that pertain to our waking lives, as well as to an alternate, archaic life with its own language and ideas transcending physical reality.By studying various myths and folk tales, along with cinematic portrayals of otherworldly experiences, commentary from modern individuals, and reports from traditional shamans who are experts at traversing the Otherworld reality, this text discerns the features and characteristics of this supernatural realm. Contemporary research into the Otherworld marks this realm as corresponding to the unconscious substratum of the human psyche, what C.G. Jung referred to as the collective unconscious. Certain scientists have found evidence of its connection with various aspects of brain functioning, suggesting that the brain in many ways encourages a belief in the Otherworld. However, it would be a mistake to call the Otherworld a figment of the human imagination, since this realm seems to have a type of physical existence. The book considers the Otherworld to exist and provides reasons why rational-thinking individuals are hesitant to accept its existence even when their brains are telling them: the Otherworld is real, and you have just experienced it.