In 1900, Greek sponge-divers detected close to the small island Antikythera the wreck of a Roman ship, which was closely investigated few months later by archaeologists. The shipwreck was dated to 80 - 60 B.C., whereas most of the valuable cargo of the ship - statues and coins - dates before the 2nd century B.C. Among the articles found there was an object with numerous cog-wheels, scales and inscriptions, which was dated to 150 - 100 B.C. and is known today as the "Mechanism of Antikythera". Since its discovery it has been interpreted as astronomical equipment, as an astrolabium or planetarium, or as navigational device, and even as a combination of a variety of such instruments. Research over more than 100 years found that the "Mechanism of Antikythera" is the oldest astronomic and calendaric computer known to date, and hence the oldest known computer in human history. The mechanism is in the National Archaeologic Museum in Athens, where the three greatest fragments are on exhibit, and the remaining 79 smaller fragments lie in the museum depot. On display here is a replica made to scale.