[ncmncm]

All we can really be sure of is that they are at least 2500 years old. But we know at least some of the white facing stonework was done about then, because we have (!) actual documents from a foreman.

There is a very great deal we still don't know about Egyptian stonework, and how it was done, that historians are aggressively not interested in discussing. Anyway what they insist was done is physically impossible. So, there is plenty left for our grandchildren still to puzzle out.

The Egyptians loved cutting tunnels, and new tech will help us locate the miles of still unexplored tunnels crisscrossing the sites.