Note: this topic is from . Thanks vannrox. If you ever return to FR, heh, and haven't succumbed to Coronavirus in China, hope you see this, somehow I'd missed this and your ping!
There's a meandering robber's hole that goes from the rump of the Sphinx up into the head, some ancient or medieval attempt to find treasure no doubt. I've actually seen video (it's on a commercial VHS tape around here somewhere, please don't make me find it; I think it was the one hosted by Omar Sharif) of Mark Lehner's ascent partway through the pretty tight passage. There are, alas, no temples or large regular chambers.
Recent video coverage of a side door on the body near the paw was found to descend to a pool of water several stories down. I think it was on one of the Egyptology shows with that young Egyptian archaeologist on Ancient Aliens.
I don’t think the pool has been plumbed yet.