What is this place? I don't know—you tell me. Perhaps it is the lair of an extended family of Fomorian giants. The place could be magically windy, with all manner of strange flying creatures inhabiting its odd passages. Alternately, you could make each square represent 100 feet, transforming the place into an ancient draconian burial system.
This could be a hunting grounds, periodically swept by organized predators from both above and below. Along similar lines, perhaps these are halls of blood and carnage, where rival humanoid factions come together to fight in an ages old conflict. It could also be a long-forgotten magical forge gone awry, haunted by scores of autonomous dancing blades.
If none of the aforementioned ideas are to your liking then you could get even more extreme. Consider flooding the entire level, requiring intrepid adventurers to be in possession of magical air breathing equipment should they want to explore it. Personally, however, I like to imagine that this place is nothing more than one of the deeper levels of The Tombs.
- There are no less than ten passages leading off-map. Moreover, there is at least one set of stairs and multiple shafts and sinkholes—all leading who knows where. Thus, this map makes an excellent candidate for a junction. You can never really have enough junctions in your megadungeon.
- There are quite a few long corridors throughout. These might be covered with hideous glyphs, or they might be choked with mold and other filth.
- See that huge round chamber? What if it is not a chamber, but rather an enormous shaft descending for a half mile? See that small, inaccessible cave in the southwest? Perhaps it, too, is a shaft. Better yet, it is a cyst or geode.
Enjoy! There will be more in the same vein in the future.
The Fine Print: I am sharing this map under a Creative Commons Attribution-Noncommercial-Share Alike license. If you follow that link you will be able to read about the conditions that apply to this work. In a nutshell: (a) you can't use it commercially, (b) you must attribute it to me, and (c) you must share any derivative works that you create.