Most technologies that are “lost” only got lost because we forgot the exact method. Greek fire is a good example; the mystery is in the exact recipe, because there’s no way to figure out which of the dozen possible ways they actually used. Today, we have stuff like napalm that does the same thing. That’s the case with most “lost technologies”: they are “lost” because we can do it better now.

But one thing we can’t quite figure out even how they did it is some of the most intricate ancient gold filigree. Some of it is so detailed that they believe it must have been made by children, because the details are too fine to even make out with an adult eye! An alternative explanation is that they had figured out that clear glass or polished quartz crystals have magnifying properties; the thing is that the craftmanship is so good it should have taken years to learn the skills, by which time their eyes should have been too large to make out the details.