Antikythera mechanism

Science & Technology at Scientific Unique Marvel of Ancient Greek Technology Gives Up New Secrets — The most complex piece of machinery until medieval times ticked off the months until eclipses and might once have shown the positions of the planets.
Both in Scientific American (linked above) and in an NPR story is mentions of the recent discoveries involving a Antikythera mechanism that is 2000 years old, found at the bottom of the Mediterranean several decades ago.
It literally is a primitive calendar computer, the likes of which wasn’t reproduced after the fall of the Roman Empire for a millennium afterwards.