The Colour of Magic

The story takes place on the Discworld, a planet-sized flat disc carried through space on the backs of four gargantuan elephants – Berilia, Tubul, Great T'Phon and Jerakeen – who themselves stand on the shell of Great A'Tuin, a gigantic sea turtle. The surface of the disc contains oceans and continents, and with them, civilizations, cities, forests and mountains.