Beliefs in mysterious underworlds are as old as humanity. But the idea that the earth has a hollow interior was first proposed as a scientific theory in 1691 by Sir Edmond Halley (of comet fame), who suggested that there might be life down there as well. Hollow Earth traces the surprising, marvelous, and just plain weird permutations his ideas have taken over the centuries. From science fiction to utopian societies and even religions, Hollow Earth travels through centuries and cultures, exploring how each era's relationship to the idea of a hollow earth mirrored its hopes, fears, and values. Illustrated with everything from seventeenth-century maps to 1950s pulp art to movie posters and more, Hollow Earth is for anyone interested in the history of strange ideas that just won't go away.