Monolith (Space Odyssey)
In Arthur C. Clarke's Space Odyssey series, Monoliths are machines in black cuboids whose sides extend in the precise ratio of 1 : 4 : 9 (12 : 22 : 32) built by an unseen extraterrestrial species whom Clarke dubbed the Firstborn and who he suggests are the earliest highly intelligent species to evolve in the Milky Way. In the series of novels (and the films based on these), three Monoliths are discovered in the Solar System by australopithecines and their human descendants.