This book is about legends of the Hollow Earth and other underground cities and civilizations which might all be related. The concept of there being a hollow Earth or inner area of the Earth where people have lived and do still exist has been around for hundreds of years. Other stories and legends of underground cities are also discussed to show that there are many stories of people and other beings living underground in our past and maybe up until the present era. Usually there is some fact as the basis for legends so all these stories make we wonder if there is some reality about civilizations existing underground on this Earth. These legends are geographically diverse and from different cultures so maybe there is something to them. Near the end of the book I include some incredible science data about life actually existing miles under our Earth and an example of a real underground city we know about and have visited.