A 2,000-year-old bronze device is considered the world's first known analog computer.

Divers recovered the corroded remains of the Antikythera mechanism from a Roman-era shipwreck off the Greek island of Antikythera in 1901, but it took decades of X-ray and CT imaging to understand what they’d found: a hand-cranked bronze device containing at least 30 interlocking gears, built sometime between 150 and 100 BCE.

The mechanism could track the positions of the sun and moon, predict eclipses, and even display the four-year cycle of the ancient Olympic Games, all through purely mechanical calculation. Nothing else of comparable complexity is known to have been built again in Europe for well over a thousand years, which is why it’s often called the world’s first analog computer.