We're all familiar with the strange, enormous chevron vault high above the entrance to the Great Pyramid at Giza. And since 2016, many of us have waiting anxiously to find out what might be behind it (after a scan that year revealed evidence of a void).
In this fascinating History for Granite video, they meticulously lay out the engineering details of the arch (and other aspects of the pyramid's construction) and offer up a convincing theory for what might explain both of them.
Spoiler alert: They posit that this archway was simple a series of experiments that were later applied to vaults inside the structure (and the void might just be a short corridor constructed as part of that experimental building process).
Not very sexy, but there ya go.