The Antikythera mechanism is a 2,000-year-old mechanical model of the solar system found in a sunken ship in the Mediterranean in 1901. It looks like a clock mechanism, but the strange thing is that there were no clocks yet at the time, so a puzzle is why, if the ancient Greeks or whoever built this had this technology, why didn’t they also have clocks? It is also a puzzle because scientists haven’t been able to recreate it using any known manufacturing technology available at the time. I’m not saying it was aliens, because the model shows the sun and other known planets (no telescopes until about 1600) revolving around the Earth, and spacefaring aliens would presumably know better, unless they were trying to trick us.