Castle Greyhawk Caverns
In 2009, Jeffs Gameblog posted an image of what is purported to be some of Gary Gygax's maps of Castle Greyhawk.
After enhancing two other maps from Gary (See Two Levels of the Real Castle Greyhawk). I came to the conclusion that Greyhawk probably looked like the TSR Geomorphs released in 1976.
If the above image is one of Gary's creations, it certainly meshes well with the the Dungeon Geomorphs Set Two: Caves & Caverns by Gary and Ernie Gygax.
Here is an enhanced image of the top map.