I've just seen one of the most visually impressive movies ever.
My friend is an animator and loaned me his copy without telling me anything about it other than "just watch it". The movie is called "The Deadly Invention" (1958). Highly impressive visuals for an old movie I've never heard of.
I found out that it's available on YouTube (unfortunately without any English subtitles). Here it is for reference: https://youtu.be/mjcEqJSpxAw