>>715625008
I'm disappointed it took this long before it was mentioned, but more so that nobody mentioned Marathon yet, especially Infinity. The narrative, architecture, lighting and especially sound design comes together to make very convincing megastructures. The low humming of obscured machines hidden deep within the structure gets me every time.
I recommend each and everyone to at least play the first level of Marathon Infinity, pic rel, it's free and now even on steam. You could be playing it within one minute.