The biggest dungeon you know of?

[delericho]

I would tend to say that they don't count, because the OP is looking for a map he can work from.

But I think even the mapped areas of Undermountain are larger than WLD.

Good to know. And agreed on all points.

 

[Ancalagon]

I used maps of the Citadel of Aleppo as a dungeon once... Players ended up freeing Joscelin III from Nur ad-Din and recovering an ancient artifact from the temple of Hadad.