Niels Klim's journey under the ground
 being a narrative of his wonderful descent to the subterranean lands; together with an account of the sensible animals and trees inhabiting the planet Nazar and the firmament.

by Ludvig Holberg

"Niels Klim's journey under the ground" by Ludvig Holberg is a satirical science-fiction novel published in 1741. When a curious philosophy student investigates a mysterious cave in Bergen, he falls through the earth and discovers an inner world orbiting a subterranean sun. There he encounters walking, talking trees, explores utopian societies with radically different values, and faces exile for challenging their customs. His twelve-year journey through this underground realm becomes a biting commentary on religion, government, equality, and human nature.