The monolith - a Space Odyssey icon

Monoliths are advanced machines built by an unseen extraterrestrial species that appear in Arthur C. Clarke's Space Odyssey series of novels and films. During the series, four monoliths are discovered in the solar system by humans and it is revealed that thousands if not more were created throughout the solar system, although none are seen. The subsequent response of the characters to their discovery drives the plot of the series. It also influences the fictional history of the series, particularly by encouraging humankind to progress with technological development and space travel. The first monolith appears in the beginning of the story, set in prehistoric times. It is discovered by a group of hominids, and somehow triggers a considerable shift in evolution, starting with the ability to use tools.