As a
consequence of the Sphinx being made in what is probably a
man-made ditch, dug as part of the quarrying work to get
limestone blocks for the pyramids, the sphinx lies below what is
the natural ground level. It doesn't obviously seem this way as
the area is a natural slope.
When
the Temple of the Sphinx became neglected and the pharaohs'
power was spent, the desert started to come back again, burying
the Sphinx up to its shoulders and restoring the ground level to its natural
position.