A mushROOM!
Armillaria ostoyae fungus, also known as the honey fungus, is the world largest organism and covers over 2300 acres!
Does a factory count? If so… https://en.m.wikipedia.org/wiki/Boeing_Everett_Factory
Factories will win this hands down, especially when you’re building large/complex items. It looks like the distinction might be “single building” vs “complex or buildings”, but VW’s Wolfsburg plant is 70 million square feet. The largest plant I’ve been to isn’t on that list, but it’s still over a half mile wide - all under a single roof.
I went looking but couldn’t find a reference. US Air Force Plant 4 in Fort Worth (where the F-35 is assembled) was at one point the longest length building without internal support columns. I’ve been told that there is a twin building somewhere else, but the one in Texas is 25 feet longer. I just can’t find a source with the number!
Probably The Asylum.
Admittedly, The Asylum has a quite a few rooms within it, but I’d say that the antechamber of The Asylum that abuts the outer wall to Outside comprises the majority of the surface of the Earth and its atmosphere, so that’s a pretty big room.
Yer mum’s rectum!
Nah I don’t know
The inside of the asylum from hhgtg
Would the super kamioka in Japan count?
