There have been rumors of passageways and secret chambers surrounding the Sphinx and during recent restoration work several tunnels have been re-discovered. One, near the rear of the statue extends down into it for about nine yards. Another, behind the head, is a short dead-end shaft. The third, located mid-way between the tail and the paws, was apparently opened during restoration work in the 1920's, then resealed. It is unknown whether these tunnels were constructed by the original Egyptian designers, or were cut into the statue at a later date.
Many scientists speculate they are the result of ancient treasure hunting efforts.
Several attempts have been made to use non-invasive exploration techniques to ascertain if there are other hidden chambers or tunnels about the Sphinx. These include electromagnetic sounding, seismic refraction, seismic reflection, refraction tomography, electrical resistivity and acoustical survey tests. These could be interpreted as chambers or passageways, but they could also be such natural features as faults or changes in the density of the rock. Egyptian archaeologists, charged with preserving the statue, are concerned about the danger of digging or drilling into the natural rock near the Sphinx to find out if cavities really exist. That's the modern riddle of the Sphinx the Egyptian authorities must solve.