But these so-called "dungeons"? No captives. Not even any cells. That's not a dungeon. that's a glorified cave.

I've always wondered how the term "dungeon" as it's used in RPGs came to be. a lot of appendix N literature had locations we would now consider dungeons, but were they called that at the time? and then the first RPG dungeon was the literal dungeon under Blackmoor Castle, but very early on we had dungeons that stopped being literal dungeons- didn't B1 and B2 exclusively have cave "dungeons?" and the Ruined Tower of Zenopus in the first Basic book had underground portions but I think those were caves too!