Lost race

The lost world is a subgenre of the fantasy or science fiction genres that involves the discovery of an unknown world out of time, place, or both. 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 the fascinating remnants of lost civilizations around the world were being discovered, such as the tombs of Egypt's Valley of the Kings, the semi-mythical stronghold of Troy, the jungle-shrouded pyramids of the Maya, or the cities and palaces of the empire of Assyria. Thus, real stories of archaeological finds by imperial adventurers succeeded in capturing the public's imagination. Between 1871 and the First World War, the number of published lost-world narratives, set in every continent, dramatically increased.

The genre has similar themes to "mythical kingdoms", such as El Dorado.

King Solomon's Mines (1885) by H. Rider Haggard is sometimes considered the first lost-world narrative. Haggard's novel shaped the form and influenced later lost-world narratives, including Rudyard Kipling's The Man Who Would Be King (1888), Arthur Conan Doyle's The Lost World (1912), Edgar Rice Burroughs' The Land That Time Forgot (1918), A. Merritt's The Moon Pool (1918), and H. P. Lovecraft's At the Mountains of Madness (1931).

...
Wikipedia