Complete tangent but this sent me down an interesting rabbit hole reading about the Celts. I had no idea they (probably) originated in central Europe, I'd assumed what we now call the Celtic nations were the origin.
Alps and neighbor Jura Mountains are still where all the major glass/crystal factories still are (Baccarat, Lalique, Daum, Gallé, Saint-Louis, etc.).
If I recall correctly the reason is that they had access to sand and lots of wood.
https://en.wikipedia.org/wiki/Celts