Hollow earth was a surprisingly popular idea in the 1920s, and while we all know Jules Verne, there were many other hollow earth stories written afterwards into the 1930s and 40s, even into the 50s a little (though by then it had lost most of its desire, since the Nazis had gone so hard into those tails, and the scientific discoveries of plate tectonics). Lol I have a hollow earth story-concept up on my website, and I call the hollow earth caverns 'Vernian Chambers', split into three different eras: the Vernian era, the 1920s and then modern stories.