The Antikythera mechanism is an ancient mechanical computer designed to calculate astronomical positions. It was recovered in 1900–01 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.
The degree of mechanical sophistication is comparable to a 19th century Swiss clock. Technological artifacts of similar complexity and workmanship did not reappear until the 14th century, when mechanical astronomical clocks were built in Europe.
Via: My Confined Space