The lost world is a subgenre of the fantasy or science fiction genres that involves the discovery of an unknown Earth civilization. It began as a subgenre of the late-Victorian adventure romance and remains popular into the 21st century. The genre arose during an era when Western archeologists discovered and studied civilizations around the world previously unknown to them, through disciplines such as Egyptology, Assyriology, or Mesoamerican studies. Thus, real stories of archaeological finds inspired writings on the topic. Between 1871 and the First World War, the number of published lost world narratives, set in every continent, increased significantly. The genre has similar themes to "mythical kingdoms", such as Atlantis and El Dorado. Source: Wikipedia (en)