|The Great Stone Face vs The Great Stone Skull|
Recently I learned that the famous rock formation known as The Old Man of the Mountain was also referred to as The Great Stone Face. The Old Man, which unfortunately collapsed in 2003, was located on Cannon Mountain in the White Mountains of New Hampshire. Nathaniel Hawthorne traveled to the area in 1832, which later inspired him to write the short story, The Great Stone Face (1850). Incidentally, Hawthorne was a favorite of H.P. Lovecraft as related in his celebrated essay Supernatural Horror in Literature.
The Great Stone Face was a mimetolith, a natural rock formation that resembles another object such as a face. Here in Holmes-country, our most famous rock-face is the Great Stone Skull in the Sample Cross Section (pg 38), colloquially known as Skull Mountain. In the past I've assumed the Skull to be carved rather than natural, but an alternate origin could have the site for the dungeon being chosen because of a pre-existing mimetolith. The evocative 1950s postcard of the moonlit Old Man shown above could even be used as an illustration for a Skull Mountain type-dungeon.
Comparing the Old Man and the Skull, we see that each appears in a left-facing profile at the top of a mountain. In fact, the Old Man could only be seen when viewed in this direction. And the phrasing of "Great Stone Face" is very similar to "Great Stone Skull". I've previously noted that the exact phrase "Great Stone Skull" appears in Shadows in the Skull, a 1975 Conan sequel by de Camp and Carter. In the 1940s, de Camp attended a Naval Training School at Dartmouth in NH, about one hour from the Old Man. There's no direct evidence that the Old Man inspired either the Conan story or the Cross-Section, but the similarities are intriguing.
Another "Great Stone Face" appears on page 30 of the Greyhawk Supplement (1975) by Gygax and Kuntz:
This drawing, apparently by Gygax himself, brings to mind an Easter Island moai and is not further explained, although page 62 includes the following in a list of Tricks and Traps:
"A great bas-relief face which if looked upon will either bestow some worthwhile
knowledge or increase to the beholder or else cause him to save versus magic or else
be turned into a wart on its face or something similar (see A. Merritt's FACE IN THE
ABYSS for a good example)".
The reader might conflate these two conceptions, and one sentence in the Face in the Abyss (1923) does describe the titular face as the "great stone Face", but the consensus is that the "Enigma" and "Bas-relief face" were two separate locations in Castle Greyhawk.