https://www.youtube.com/watch?v=YTgxGJfXRQ0 The premise of Jean-Pierre Houdin is that there are undiscovered internal tunnels in the Great Pyramid (and presumptively the other larger pyramids) that were used for the construction. If nothing else, these are interesting computer animations of his theory. It remains unproven. Surprisingly, nothing is said about the neighboring Kahfre pyramid, which is nearly the same size and would have required similar construction. We should know in a few years whether there is merit to his suggestion.