The conclusion from various experiments conducted around the Great Sphinx at Giza, Egypt by several investigators over the years remains a mystery. But why is that? Is it because the non-invasive methods used to detect natural or man-made underground spaces produced false positive readings not verifiable by invasive tests like drills and audio or video probing, or is it because the right area has not been probed? It depends on who you ask.
According to the comments made in this video, the case is closed. This particular drill was made here:
But was this location the best possible one to put to a test what non-invasive studies conducted in the 1970's (Stanford Research Institute International), 1980's (Waseda University, Tokyo, Japan), and in 1990 (Thomas Dobecki and Robert Schoch) predicted?
And then we have the strange case of unexplained holes in the Sphinx Temple such as these:
Where these the holes made in the 1950's by two ladies written about by Robert Bauval in Secret Chamber Revisited: The Quest for the Lost Knowledge of Ancient Egypt?
And finally, we have this:
However you may wish to characterize these investigations, the sum of it does not add up to a closed case, at least not if one applies a purely scientific standard unadulterated by politics and other considerations.