Unlike the pyramids, the Sphinx is carved directly from the existing natural limestone bedrock. Egyptologists consider it to be an example of subtractive sculpturing in which the limestone was selectively removed to create the Sphinx. This method is technically more demanding than additive sculpturing, as once a section is removed it cannot be replaced. To achieve this, the artist either needs to carefully select flawless stone or find inspiration within the rock itself. Given that the facial features of the Sphinx conform with sedimentary bedding planes and the facial profile itself appears to follow a vertical bedrock fracture, I believe the artist was at least partially inspired by the raw stone. The origin, construction, erosion, and preservation of the Sphinx is intimately tied to its geologic history. That story begins 40 million years ago with the deposition of the limestone bedrock during the Eocene Epoch.