While you may have heard of the Flat Earth Society, and understand what they believe about the Earth's shape, have you ever heard of the hollow Earth theory? While the theory may have been rooted in science originally, it has since diverged to become something closer to science fiction. However, that hasn't stopped people from believing in it!
Want to find out more about the theory that's been around for more than 300 years? Click through the following gallery to learn all about the far-fetched hollow Earth theory.