The two principal locales for the novel's action are England and South America.

In England the action takes place amid the closed-minded and stodgy scientific establishment. The outrageous Professor Challenger seems out of place among these small-minded, boring people and the continent of South America seems better suited to his expansive personality. The jungles there are dense and dangerous, and the native inhabitants are generally friendly.

By following an old map, Challenger leads his expedition to the Lost World, a great plateau with sheer cliffs all around. On the plateau, life has changed little since the age of dinosaurs.