Pyramids Are Not What You Think They Are: Underground Halls Beneath Them According to geological evidence, the Sphinx was not 4,500 years old, as was commonly accepted, but much older, in fact, over 10,000 years old, dating back well before the rise of Egyptian civilization as we know it. Further, seismic surveys showed a vast expanse of unexplored tunnels and chambers underneath the Sphinx, stretching deep underground. Documentary viewers and historians a cross the world wondered what this could mean, what secrets could be hidden in these unexplored depths.