There's apparently a giant void in the Great Pyramid. Here's why we don't know what's in there.

In addition to seeing the already-explored King's Chamber, and confirming an earlier observation, they also saw a large, nearly 100-meter-long void in the pyramid, isolated from the previously investigated chambers. Its huge size is intriguing to researchers who would like to know more about how the pyramids were constructed. Only fragments of evidence of building techniques remain. It's unclear what the void is, and the researchers are careful not to call it a room or a chamber. As Egyptologist Mark Lehner told multiple outlets including the New York Times, finding holes in a pyramid isn't exactly rare.