Astoundingly intricate astronomical mechanism retrieved by divers from 45 metres (148 ft) of water in the Antikythera shipwreck off Point Glyphadia on the Greek island of Antikythera (pronounced an-ti-KEE-thur-a) in 1901, and subsequently dated to sometime in the first two centuries BC.

Archeology recovers a certain picture of the past, but can be lopsided if taken to give the full picture! Too much of the past has simply not survived the rigors of time as we realize when things like this miraculously do survive. Ancient writings mention devices like this, but none of them or their plans have survived.

Exploded computer reconstruction of the Antikythera Mechanism

"On the left, the front plate includes zodiac and calendar dials and a conjectural reconstruction of the ancient Greek Cosmos. In the middle is an exploded reconstruction of the gears. The input contrate gear is in the centre, with a keyway to turn the Mechanism. The planetary gearing at the front is conjectural, but the gearing behind the main plate for the lunar anomaly mechanism and the back dials is now firmly established. On the upper right is the 19-year Metonic calendar dial and on the lower right, the 223-month Saros eclipse prediction dial."

A schematic representation of the gearing of the Antikythera Mechanism, including the latest published interpretation of existing gearing, gearing added to complete known functions and proposed gearing to accomplish additional functions, namely true sun pointer and pointers for the five then-known planets, as proposed by Freeth and Jones, 2012.

Describing the genesis of this computer reconstruction, here is the research paper written by Tony Freeth and Alexander Jones:

The Cosmos in the Antikythera Mechanism

This video is a tribute from Swiss clock-maker Hublot and film-maker Philippe Nicolet to this device, known as the Antikythera Mechanism, or the world's "first computer":

Wikipedia article on the Antikythera mechanism

Virtual model of the Antikythera Mechanism by Mogi Vicentini based on the theoretical and mechanical model by Michael Wright:

Washington Post Article: The world’s oldest computer is still revealing its secrets

Smithsonian Article: Decoding the Antikythera Mechanism, the First Computer

Quote from the end of the above article:

Antikythera mechanism proves that the ancient Greeks used complex arrangements of precisely cut wheels to represent the latest in scientific understanding. It’s also a window into how the Greeks saw their universe. They came to believe that nature worked according to predefined rules, like a machine—an approach that forms the basis of our modern scientific views. Edmunds argues that this “mechanical philosophy” must have developed as a two-way process. The ancient mechanics who captured the cosmos in bronze weren’t just modeling astronomical theories but were also inspiring them.

NOVA Documentary: Antikythera Mechanism The Two Thousand Year Old Ancient Computer: