The Land That Time Forgot is an Edgar Rice Burroughs science fiction novel that starts out as a nerve-wracking wartime naval adventure but develops into the story of a unique and mysterious prehistoric lost world, as a submarine enters a subterranean passage under the sea and emerges into a tropical world sustained by volcanic heat. The first novel in the Caspak trilogy, The Land That Time Forgot is followed by The People That Time Forgot and Out of Time's Abyss.