Speaking of "generic D&D," I've decided there's a megadungeon beneath the city. As much of a cliche as its become at this point (the classic example being Undermountain and Waterdeep), I really like the idea of big dungeons being directly underneath currently inhabited cities, as opposed to some ruins somewhere. There's something about having a vast underground world full of monsters, magic and treasure directly just a few miles (or whatever, I'm terrible with relative distances) below where your players' characters hang their hats, something that really emphasizes the weirdness of the dungeon as a concept. We're all comfortable with the idea of cities having a certain amount of their existence underground - just not that much; it makes the familiar strange, if I can put it in those overused terms. And the city itself becomes richer and deeper, because you have to account for why the fucking thing is there in the first place.
In my case, I'm pretty much just writing an Undermoutain fanfic and adding some Norse and Cthulhu Mythos flavour. Call me unoriginal, but there's something about Forgotten Realms and the Underdark that really speaks to my soul, so I want to strongly ape that vibe, with a sprinkling of some of my other influences. Think of it as some intermediate step between concocting a wholly original world and just straight-up running a Forgotten Realms campaign. You could argue that there's no real benefit to not just doing one or the other, and maybe you'd be right, but this is what's in my heart.
So: Silfurfall was built on top of the underground ruins of Dregypth, an ancient dwarf city. Once the capital of the Dwarven Empire, it was almost entirely destroyed during the thousand-year civil war which eventually split the Empire into the Five Kingdoms. The leaders of these new states opted to move their seats of power elsewhere and abandon the ruined Imperial capital, both out of the practical consideration that it just wasn't worth the effort to rebuild, and out of concern to leave a symbolic reminder of the high cost of war.
That was several thousand years ago. The Five Kingdoms have since semi-reunited to form a kind-of Empire again (they're still technically separate kingdoms, but are governed jointly by a council made up of all five kings), and the ruins of their ancient capital have gone through various changes as well. Shortly after it was abandoned, the lower sections were taken over and rebuilt by a kingdom of enigmatic Dark Dwarves, who ruled over it and warred with their "good" cousins for a few centuries before themselves abandoning the place, for unknown reasons. Before this, they managed to construct several levels' worth of dungeon complex beneath their repurposed home, which they used as a prison and a place to exile political enemies; it still contains ancestors of these (or in some cases the originals). Over the centuries, these levels were expanded and added to by various groups: dark elves, sinister cults, mad wizards, and some even stranger beings and races. Each of these areas or levels bears the mark of its original inhabitants, some of whom live there still.
The dungeon isn't a secret or anything; everyone knows about it, though many probably don't suspect just how deep and extensive it is. It's just another thing that makes Silfurfall a thriving commercial centre: between the giant dungeon underneath and being the gateway to uncharted lands past the mountains, Silfurfall would probably have one of the biggest concentration of adventurers of anywhere in the world, if not the biggest. It's what this guy calls an "open dungeon": it's known, it's well-trafficked by adventurers, and as such contributes significantly to the local economy. The first few levels, then, will be significantly emptier of monsters and treasure than the lower ones, with the most interesting stuff around the fringes, away from the main entrance. Of course, these more trafficked areas will have their own interest: it would make sense for adventurers to have set up one or more semi-permanent camps, perhaps even officially sanctioned and protected by the city authorities and/or the dwarves.
One advantage of placing the dungeon right underneath a city is that it opens up a bunch of logical ways to have multiple entrances: there's the "official entrance," but then the city sewers connect up at some point as well, as do Castle Ormor's dungeons and the cellars of a secret temple of Tsathoggua. Other ways in include the dwarven mines, and probably several caves or dens out in the wilderness somewhere, to help explain how random monsters like orcs, goblins and dragons have managed to get in there. Some or most of these will hook up to levels other than the first; as they're discovered, it will be easier to skip lower-level explored areas and get right to the good stuff, as received wisdom suggests is essential for a good megadungeon.
Each level will be vaguely themed, with the first few being built right into the premise: 1st level is the ruined dwarf city, 2nd level is the abandoned dark dwarf city, and the next few are the dungeons the dark dwarves built. After that, we can have areas or even whole levels that are dark elf kingdoms, or mad wizard's laboratories: all that essential shit. The deeper levels will be weirder and more overtly Lovecraftian; I have a vague idea that one of the lower levels hooks up to Cthulhu's island-prison of R'lyeh somehow, though don't ask me how that works.
The other day I was reading about how Gary Gygax apparently designed a level of the Greyhawk dungeon every week, for a total of thirteen levels. I've been thinking of doing something similar: a week to map and key a 70-100 room dungeon level seems fairly reasonable, if I stick to relatively minimal keying (which seems to be what Gary and all those other old-school guys did, keeping most of the dungeon in their head and/or developing it during play). Eight or nine proper dungeon levels, plus sub-levels to get me up to Gary's thirteen (I may or may not count the alternate means of egress as sub-levels: the palace dungeons, the cult cellars, etc., which means I might end up shooting higher than thirteen, but we'll see).
So there you have it. I promise I'll go back to talking about slimes again soon. Oh, and as long as I have you here, check out my friend Jastrick's new blog, which is miniatures/wargaming focused but which he tells me will include thoughts about tabletop games in general. It's looking good so far! Jastrick is one of the players in my Roll20 game, which started out being about exploring the Crater of Termination but has turned into me running Tegel Manor... but that's a story for another post.