The book "Underworld" by the author Hartwig Georg tells about the exciting discoveries that await a person in the unexplored underground world. The author describes in detail the uniqueness of underground landscapes, mysterious caves, mysterious human structures that are still unknown to science. The book gives the reader the opportunity to see the underground world from a completely different angle, revealing its secrets and mysteries. "Underworld" is an exciting journey to the deepest and most secret corners of the Earth, which will leave behind unforgettable impressions and new knowledge.