In the 1900’s some Greek sponge divers came across a clock-like mechanism in a shipwreck near the Greek island of Antikythera.
On further examination this mechanism was found to be one of the most complex scientific mechanism of ancient times ever discovered.
Dated to the 2nd century BC it is a small brass device.
For the last many decades this mechanism, named after the island where it was found - Antikythera Mechanism- was a puzzle for scientists and archaeologists world over. This mechanism was being studied under the Antikythera Mechanism Research Project, which was a joint program between many universities and supporting corporations across the world.

One of the teams was that under Mike Edmunds from Cardiff University, Wales, they have shown that this mechanism could predict the Saros cycle, which is a period of 18 years when the Earth, Moon and Sun come to the same relative position, from this information solar and lunar eclipses can be predicted.

There are many records of ancient mechanisms as complex as Antikythera mechanism however they have never been found.
As Edmunds puts it, “The real significance of this is just how sophisticated the device was - much more complex than a modern wristwatch. It is beautifully designed and must have come from a long tradition of making these kinds of devices.”

Ref: Wikipedia on Antikythera Mechanism

Source: New Scientist Tech