Grand Necropolis (Megadungeon?) [Battlemap]
Here is a very large battle map of a Necropolis-type dungeon. I'm not sure if it is quite big enough to be a true megadungeon, but it is up there.
I based it on the plans of actual Ancient Egyptian tombs from the Valley of the Kings rendered as accurately as I could squared off for the grid. (You can see recognizable parts of KV 5, KV 7, KV 17, KV 21, KV 3, KV 43 and KV 14 if you care).
I know that there is an awful lot of black in this image, since it is the raw image from maptool, stitched together in Photoshop. I will fiddle around with it and try to make a cleaner, printer-friendly version.