Pellucidar

Pellucidar is an adventure and science fiction novel written by Edgar Rice Burroughs and first published in 1923.

The story tells of the adventures of David Innes and his friend Abner Perry, who manage to break through the Earth's crust with the help of a remarkable machine and reach a strange prehistoric world that exists inside the Earth, called Pellucidar.

In this new world, they discover that the sun is constant and never sets, so there is never night, and that it is inhabited by prehistoric creatures, including dinosaurs, as well as primitive humans and other intelligent species.

From here begins a series of adventures and dangers with several different races of creatures and a totally different world that they will encounter.

"The Arabs, of whom I wrote you at the end of my last letter (Innes began), and whom I thought to be enemies intent only upon murdering me, proved to be exceedingly friendly—they were searching for the very band of marauders that had threatened my existence. The huge rhamphorhynchus-like reptile that I had brought back with me from the inner world—the ugly Mahar that Hooja the Sly One had substituted for my dear Dian at the moment of my departure—filled them with wonder and with awe."