There are a number of them but this one concerns the Serapeum of Saqqara located around 14 miles West of the pyramids in Giza. Within these catacombs are some 20+ mysterious block boxes. Therein lies great mystery.
These black granite blocks appeared to have been hollowed out forming a box and polished Some weighing more then 200,000 pounds.
The polished surfaces are completely flush with corners accurate down to millionths of a meter. The granite itself imported from over 800 miles away. This gives rise to those who believer ancient aliens visited Earth.
I'm not to sure about that but it sure does cause someone to ponder a few things. The tunnels at Saqqara date back earlier then 1213 BCE. This being the case...
Video Courtesy: Brien Foerster-- khemitology.com/
Seems to me this is another case of the more you learn-- the less you know.