Dark Souls has a bit of a reputation for being a difficult game.
Without increasing the difficulty setting, how, then, does it get even harder?
By removing the walls and floors, of course!
The YouTube user who found this bug was simply going about his business before he encountered this phenomenon, dubbing it "Super Secret Hard Mode". Fitting, I think. Interestingly, this glitch is not an instance of just falling through the map, but the barriers simply disappearing. The player is still guided by the walls and floors that should be visible, and objects are floating in place.
Only the truly skilled gamers could navigate this invisible maze. That, or a lot of trial and error, as seen in the video.
He almost makes it, too, until a hidden cliff suddenly puts an end to his run. I doubt this can be replicated, but it would be cool to see if a player could successfully make it through alive!