Pellucidar

By Burroughs Edgar Rice

Pellucidar is a fictional Hollow Earth milieu created by Edgar Rice Burroughs for a series of action adventure stories. Its internal surface is a perpetual twilight illuminated by a miniature sun at the center of the hollow planet. It is populated by prehistoric creatures (dinosaurs, mammoths, etc.). The stories involve the adventures of mining heir David Innes and his inventor friend Abner Perry as they search for a way to the surface world.