What are you doing down here?! You can't be . . . Oh, yes, you can. Thought you were house-elves, for a moment there. I mean, not that house-elves can't be below ground, I mean, that's where they live, isn't it? No, but they can't, they mustn't be down here in the Dungeons. Dangerous place. No telling what might be loose.
Mind you, it doesn't bother me. The upside of being a ghost. Four hundred year-old vision, true, but there's not many threats to my health. Then again, I remember that nasty business with the Basilisk. Twice, as a matter of fact. Slithered out of the Chamber of Secrets, which is meant to be somewhere hereabouts, by the way, and munched its way through the student body. Well, alright, mild exaggeration, but it gave most of us a real scare, and that is the truth.
So anyway, besides the theoretical Chamber, there's a lot of very real rooms and nooks and corridors. All sorts of places for bumpy things, and things that go bump. There's all the Potions-related places, the Classroom, Professor's Office, Basement - and don't think, just because people aren't brandishing wands wildly that it can't be a deadly place, some of those poisons . . . Anyway, there's all that and, of course, the Slytherins.
Oh yes, the Slytherins are down here. All the time, in fact. Got their Common Room under the lake, and I've heard one of them once tried to put an Unforgivable Curse on the Giant Squid. Not likely to come to much, in any case. Too big, too magic resistant. Still, it takes a certain something to even think about an attack like that. It makes you wonder. Mind you, they say lapping water's very restful, you know, for those of you who have to sleep.
And, of course, where you've got their Common Room, next door you've got their Head of House. See, even Slytherins know better than to trust other Slytherins, so the Head's always breathing down their necks.
Funny image that, a head breathing down its own neck. How would that work, d'you think? Really ought to ask Nick, I suppose.
Anyway, as I said, lots of stuff down here in the Dungeons, Kitchens just above, but still below the Great Hall, don't you know, and in the Basement with them is the Hufflepuff Common Room. Rum sort, Hufflepuffs, never quite know where you are with them. Friendly and helpful enough normally, but when you get their backs up they've got a hard centre you'd never look for in such easy-going folk. But still, you can trust a Hufflepuff, that's been my experience. Four hundred years of it, as I said. Their consciences must be clear, because when they drop off, you certainly hear it.
Beyond that, naturally, there's the Grounds, which, surprise, surprise, are at ground level, but I'll leave someone who feels more of a need for fresh air to tell you about them.