The Antikythera mechanism is an ancient mechanical computer designed to calculate astronomical positions. It was recovered in 1900–1901 from the Antikythera wreck. Its significance and complexity were not understood until decades later. Its time of construction is now estimated between 150 and 100 BC. Technological artifacts of similar complexity and workmanship did not reappear until the 14th century, when mechanical astronomical clocks were built in Europe.
The mechanism is the oldest known complex scientific calculator. It contains many gears, and is sometimes called the first known analog computer, although its flawless manufacturing suggests that it may have had a number of undiscovered predecessors during the Hellenistic Period. It appears to be constructed upon theories of astronomy and mathematics developed by Greek astronomers and it is estimated that it was made around 150-100 BC.