The Antikythera mechanism is an ancient Greek device that was discovered in the early 20th century on the Greek island of Antikythera. It is a complex mechanical device that was used to calculate astronomical positions and predict eclipses, and is considered to be the oldest known example of a geared mechanism in existence. The device is made up of a series of interlocking gears and dials that were used to represent the positions of the sun, moon, and planets in the sky, as well as the phases of the moon and the dates of solar and lunar eclipses. The Antikythera mechanism is thought to have been built around the 2nd century BC, and is considered to be an important example of ancient Greek technology and scientific knowledge.