A 100-foot-long chamber

In 2017, National Geographic reported on what Egyptologist Yukinori Kawae called "the discovery of the century." That's quite a claim, Kawae! The Great Pyramid of Giza is the pyramid everyone thinks of when they think "pyramid," and the ScanPyramid project has been using some super high-tech gadgets and gizmos (that's the scientific term) to look inside Khufu's massive pyramid for some time now. They've seen thermal signatures that indicate voids, but that's largely been written off as a byproduct of the building process instead of being any planned interior structure. Now, they've confirmed there's a massive void at least 100 feet long positioned directly over the long hallway leading to Khufu's burial chamber, and it looks like it was intentional.
So, what is it? No one really knows, but there are a few guesses. One Cambridge archaeologist suggests the void's alignment with the massive stone blocks forming the top of the King's Chamber makes it likely the void was just left behind by the stage of construction that moved those huge blocks into place, but others disagree. Forbes says other researchers (i.e., party poopers) were quick to point out there's probably not a connection to anything super mysterious or occult-ish, which pretty much ruins our idea of archaeology. Since the void is completely sealed and there are no access points, it's unlikely we'll be finding out for sure what's inside anytime ,,