Many cultural around the word have myths and legends based on the idea that the Earth is hollow. From the ancient times, Greeks believe in the underworld and some cultures even believing that hell itself really is a fiery place beneath the Earth’s surface.
To modern beliefs that great kingdoms exist down below, there has always been speculation about hollow Earth theories. Evidently, there are subterranean cities beneath the Earth’s surface, where many strange races of people live. Some of cource believe that UFO is come from these cities, where they were built by engineers with advanced technology.
