Just finished watching Raw Meat (Death Line in the UK). I've been hearing about this movie for years from both my parents. See, when we start talking about obscure and bizarre movies, this one always comes up. They saw it on one of their earliest dates, and couldn't remember the title. All they could remember is that it involved cannibals in the sewers, and that all they could say was "Maah dee daaaah"
So I found it, through a guy I work with who is also all about obscure music and movies. It's all that's good about seventies horror, and British to boot. Kinda like the Abominable Dr. Phibes.
So back to dungeoneering, the whole movie is centered around these cannibals. Subway workers who were trapped in the 1890's and have been living off of each other and anyone they can get their hands on. So they have a sweet dungeon complex. Sweet in the "reasonable ecology of a dungeon" sort of way.
They've got living areas (well, a cot, a booze still, and lamps), a tomb (full of loot covered dead cannibals), a "pantry", a means of exit/entry, a reason for being down there, and a ton of rats.
Mainly, the dungeoneering aspect is best represented by the imagery, and reactions of the police when they get down there. Just to see how normals might react to a critter lair. Cuz these flesh eating limeys weren't too far removed from orcs, morlocks, or measels.