The Hollow Earth: The Greatest Geographical Discovery in History Made by Admiral Richard E. Byrd in the Mysterious Land Beyond the Poles (1964) by Dr. Raymond Bernard is a classic fringe-theory book that proposes the Earth is hollow, habitable, and accessible through openings at the North and South Poles. The book argues that Admiral Richard E. Byrd’s polar expeditions uncovered this inner world, which is populated by a superior civilization. The Hollow Earth is considered a cornerstone text in modern conspiracy theories regarding inner-earth civilizations and UFO origins.