The Antikythera mechanism dates back to ancient Greece around 150 BC. It was discovered in 1901, but only recently have scientists been able to examine its guts. They say it predates similarly-complex clockwork machinery by about 1,500 years. This is the first time I’ve seen a working model that isn’t just a rusted-out wad of gears:

How many more objects like this will never be uncovered? It’s sheer luck we happened to find this wearable spacetime locator beacon, clearly standard issue for the ancient Greeks’ Pantemporal Phalanx.