This series of doors by Wout12345 is insane, let's just get that out of the way. How does this work? I have no idea. Is the redstone shown and explained? Yes, and it still makes no sense to me. Is it photoshopped, or a hoax of some other sort? Apparently not - it does work as advertised - but it still defies belief.
This odd redstone door setup is apparently infinitely scalable, allowing doors as large as can be imagined. While it does suffer from one rather unavoidable setback (being incredibly slow at larger sizes, sometimes taking hours to open or close), it is nonetheless a remarkable machine!
So what do you think? Wout has provided a download link for anyone curious about its legitimacy, but even having it in front of you makes it hard to believe. Give it a look for yourself!