In 1901 Greek sponge divers found an odd looking piece of coral encrusted brass gears on the site of a sunken Roman vessel from the first century BCE. The wreck was off the coast of the island of Antikythera, near Greece, and the device has become known as the Antikythera device. The device was cleaned up, x-rayed, extensively studied, and it appears that is was a mechanical computer that displayed the position of the stars, planets, and moon.
A reconstruction of the device has been made, on paper, as computer animation, and out of brass, the material of the original device. 
The device consists of a number of geared wheels that are mounted on a bronze plate. A shaft was turned by a handle, which caused the large crown-gear wheel to turn. The crown-gear wheel moved the large four spoked drive wheel, which in turn moved two connected gears and a set of gear wheels and shafts connected to them. The movement of the gears and shafts resulted in moving three pointers on the exterior of the machine, which indicated star positions, planet positions and lunar positions. Only one dial is unobstructed by the encrusting material, and it shows a dial with the symbols of the zodiac and the months of the year.
This dial showed the position of the sun in the zodiac, and the main risings and settings of brights stars and constellations during the year. The gears were made with triangular teeth, which is a primitive type of gear, but one that could be made by a craftsman with a triangular file. The device appears to have been repaired at least twice, which indicates that it actually worked, and was used for a period of time. Its existence also indicates a technological skill that was not known to exist in that time, and did not exist in modern times until tens of centuries later.
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