Every dungeon in TES: Arena. Long, confusing, and creepy, even now, as there could be a strong enemy right infront of you but too far to see, all you'd be able to identify it by is it's noise making and possible "hitting-you-from-far-away-with-death" attacking.

The dungeon crawl before the fight in FFIII that lets you go to -spoiler- and you find out that the place you live in is really just -spoiler- in the -spoiler-.

Censored for those who never played the most frustrating FF ever.