At some point the history channel claimed that there is a room underneath the sphinx that existed since the dawn of the civilization and Egyptian authorities don't want us to know about it. As the episode continued, it became clear that the script was so bad and poorly written, that even the episode's core point, the secret room that "Egyptians keep secret", loosely stood up after just five minutes of watching.

And this is one of the many reasons that the History Channel isn't a good source for information regarding history. It is full of misinformation, conspiracy theories that look fake even from the first glance and lots and lots of "proof".