It wasn't uncommon to do this in those days, nearly all of the original DOOM's textures were taken from real life places or objects (or more rarely, people) same with the original Half-Life, it's a good time saving measure since all you have to do is downscale the image to use it in game
I did grab one of the screencaps from Twitter based on Course 11, but would love to get all the backgrounds from those places. They make neat desktop BGs!
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ok no seriously i dont really get 'mario 64 kinda spooky' thing ppl keep saying
There's a Mosque in the collage which is the Muhammad Ali Pasha Mosque in Egypt