You don't have to necessarily believe them, just find them interesting.
Hollow EarthThe idea that the Earth is Hollow and is habitable, some ideas of Hollow Earth include dinosaurs and aliens.
AtlantisThe advanced, wealthy ancient kingdom that sank in 9000 BC described by the Greek philosopher, Plato, the story also has origins in Egypt
Ancient AstronautsThe idea that aliens visited Earth in the distant past and made contact with humans and had an influence on religion.