Pellucidar

Pellucidar is a 1915 fantasy novel by Edgar Rice Burroughs, the second in his series about the fictional "hollow earth" land of Pellucidar. It first appeared as a four-part serial in All-Story Weekly from May 8–29, 1915. It was first published in book form in hardcover by A. C. McClurg in September, 1923. A map by Burroughs of the Empire of Pellucidar accompanied both the magazine and book versions.