Built on the site of where dawns light first touched the world, and occupied time and again by civilizations both ancient and recent. Any number of stories are true, from dwarves, to elves, to mages to empires to private manor; all have been true at one point of another back to the literal dawn of time. But none survive for long, and wanderers keep coming to see what others have left behind. All pass through the Black Maw.
The first level of the Black Maw megadungeon, for character levels 1-2.