The Antikythera Mechanism: A Computer from Antiquity

Recovered from a Roman-era shipwreck in 1901, this corroded bronze lump was revealed through X-rays to be an incredibly complex analog computer. With at least 30 interlocking gears, it could predict eclipses and the cycle of the Olympic Games. It proved ancient Greeks possessed a level of engineering previously thought impossible for another 1,500 years.