Sir Arthur Conan Doyle may be most famous for creating Sherlock Holmes, but he is also responsible for putting a name to the pulp/fantasy genre of the lost world novel. Professor Challenger's journey onto a plateau in South America where dinosaurs still roamed has affixed the phrase “lost world” to all such ventures into lands that time forgot, where creatures thought lost to the mists of history remain and thrive.
We are lucky to have an ancient copy of The Lost World, an edition by John Murray and co, published in 1914, complete with beautifully-faked “photographs” from the expedition, showing the mysterious plateau - I'll post scans from it in a later post.
Other writers have created lost worlds of their own, for example on Antarctic islands - Edgar Rice Burroughs' The Land that Time Forgot and sequels.
Another good place for a lost world is in chambers inside the earth. Jules Verne's Journey to the Centre of the Earth is the obvious example, but Edgar Rice Burroughs also got in on the act with his Pellucidar stories.
South America was also popular (and quickly became very crowded with supernatural creatures and regions). As well as Conan Doyle's Lost World. A Merritt's The Face in the Abyss is probably the best early contender here.
By the late 1930s, Earth was becoming crowded and the presence of dinosaurs or other creatures was becoming more difficult for writers to suggest, and so lost world-style stories moved elsewhere in the solar system.
As well as Edgar Rice Burroughs (whose heroes travelled to most planets in the solar system), contemporaries such as Otis Adelbert Kline, Ralph Farley and Manly Wade Wellman explored visions of colourful alien worlds.
As scientific knowledge grew apace the solar system became too difficult to justify. Now, the lost worlds have moved to other dimensions, fantasy lands and distant worlds. But they still have a sense of wonder about them – it is a field of fantasy that (unlike the dinosaur) is still alive and kicking, both in books and films.