I was thinking of House of Leaves reading the other comments here, mostly because something like an infinitely long tunnel to nowhere hidden in the walls of your house would actually be scary to me, whereas normally occupied spaces being empty and long winding indoor hallways are far more mundane. My wife has gotten into backrooms lore quite a bit in the past few years and it's always struck me as a strange thing to find eery. I've been an early morning runner for much of my life, worked overnight shifts at a theme park, closing at a mall, been in the tunnels beneath Disneyland and downtown Dallas. Worked in stores that hadn't opened yet and had nothing in them. There was nothing scary or eery about any of those things. It seems like an effect of the photographs and presentation more than the reality of the physical places. House of Leaves is scary specifically because it can't be real. Another example is something like the wormhole to 1987 and 1954 at the end of a cave in Dark. Yeah, that's scary, because nothing like that exists and you have no idea what to expect going into it.

Ironically enough, I first read this book when I worked at Disneyland, at an attraction with tunnel access, that no longer exists, and I no longer have the book because I loaned it to a girl I worked with there who never gave it back. She and I hung out in those tunnels during breaks.

Also interesting to me seeing other responses about found footage, given the guy who first recommended this book to me was a friend from college who covered his dorm room in bizarre free-form prose that switched between play style and novel style during a manic episode, then tore it all down later, set it on fire, and pieced together what survived as the strangest pseudo-poetry that somehow still had a lot of real words in it, kind of nature's "found poem." This book was probably written around the same time Blair Witch Project first came out and this guy also lived next to the real Greenway Trail in Burkittsville, which was also not particularly scary to see in person. I kind of doubt that was really the first example of a found footage film but it's the first I'm aware of. Wikipedia is saying The Connection from 1961 is the first.