Living inside the Hollow Earth

Hollow Earth theories come in different flavours. One states that the inside of our planet is hollow and another is that we actually live inside the concavity of another world. Italian author Umberto Eco commented recently on the hollow Earth for the New York Times.

The theory has also cropped up in science fiction on occasion, such as Jules Verne's Journey to the Center of the Earth or Edgar Rice Burroughs' At the Earth's Core. Even some Nazis believed in the theory.