The belief that the Earth is hollow can be traced back for centuries and has captivated such notable figures as Adolf Hitler and Edmund Halley. Combining scientific research with eyewitness accounts, this book seeks to answer the most baffling unexplained mysteries, such as Was this inner world inhabited before mankind set foot on the Earth's surface? Did the people of Atlantis and Mu take refuge there when catastrophe overtook them? and Do UFOs come, not from outer space, but from inside our own planet? From polar explorers' observations to satellite photographs, the scientific evidence gathered here gives credence to the mysterious legend of a hollow Earth.