Dark Souls Remastered files contain an early design of Bloodborne’s Upper Cathedral Ward.
More specifically, the Upper Cathedral Ward design has been part of the original Dark Souls release as well, meaning From Software created this early version during the development of Dark Souls, four years before the release of Bloodborne.
What's bizarre, however, is that the modder who dug them up didn't stop at this amazing discovery, they also imported them into GTA 5 of all things. The video below has Trevor exploring this early version of the level, and even driving through it.
Modder Dropoff told Kotaku that they found the design in a file titled “m99_99_98_00", noting that files that begin with "m99" are typically reserved for unfinished and test assets.
With the help of "3D software", Dropoff was able to repackage it into something GTA 5 can run, hence the video.
It's not everyday you find a level from one game in another game, and be able to extract it to run into a third game.
This may not have much value in GTA 5, but it's nonetheless an interesting look at the iteration that goes into creating locations from many of our favourite games. Perhaps the Upper Cathedral Ward had a different name during the development of Dark Souls, and it may have even been intended as part of the game at one point.