On Mega-dungeons

Mega-dungeons are odd things.

The most simple, direct definition of a megadungeon is "A dungeon that a entire campaign can be run in and around it."

Back in the early days of D&D, random, gonzo megadungeons were not uncommon, but over time more narrative play took hold, but there is still a place for Megadungeons.

Quite a few have been published - Undermountian is a big map with little filled out.  Temple of Elemental Evil is a classic example of a fully developed Megadungeon.   Over the last ten years or so many more have been published, castle of the mad archmage, stonehell, Rappen Athuk, Barrowmaze all come to mind. 

However to run a campaign of a mega-dungeon, you have to answer a few questions.

1) Why is it there?

Is this a old mine that been expanded?   Is it a old fortress?  Was it carved down, or was it carved upwards from the underdark? 

2)  Why are the upper levels not cleared out yet?

Quite simply if any adventure group could, the upper levels would be striped bare.   Is it newly discovered?  Perhaps there was some army defeated that opened the path to it.  Perhaps it was forgotten but now bands of evil have been raiding.

3)  Funhouse, Ecological,or somewhere in between?

Funhouse duneons are just whimsical dungeons that have random things thrown into most rooms.  No real rhyme or reason, Ecological design is were each location is carefully designed, with air, food, and logic dictating the design.

Or find a sweet spot in between.

4) Where will you get the maps?

Are you going to draw them yourself?  Will you use one of the many random dungeon generators?  or use someone elses maps that allow you to use them?

5) how BIG are your levels?

Are you going with a lot of small levels?   Or are you going with fewer sprawling levels?