Pellucidar Illustrated

Pellucidar is a fictional Hollow Earth invented by American writer Edgar Rice Burroughs for a series of action adventure stories. In a crossover event between Burroughs's series, there is a Tarzan story in which he travels into Pellucidar.The stories initially involve the adventures of mining heir David Innes and his inventor friend Abner Perry after they use an "iron mole" to burrow 500 miles into the Earth's crust. Later protagonists include indigenous caveman Tanar and additional visitors from the surface world, notably Tarzan, Jason Gridley, and Frederich Wilhelm Eric von Mendeldorf und von Horst.Pellucidar is lit by a miniature Sun suspended at the center of the hollow sphere, so it is perpetually overhead and gives a sensation of eternal noon wherever one is in Pellucidar. The sole exception is a region directly under a tiny geostationary Moon of the internal sun. As a result, this region is under a perpetual eclipse and is known as the "Land of Awful Shadow". The moon has its own plant life and (presumably) animal life. Basically, the moon either has its own atmosphere or shares that with Pellucidar.