Pyramid Plunder
The hidden shafts in the Queen’s Chamber of the great pyramid. Since the shafts are too small for a person to fit through, there have been two separate attempts to send in specialized robots.
The first time they sent up a robot they reached a dead end and what appeared to be a sealed door, complete with metal handles. A decade later they came back with a new robot equipped with a drill, only to find that behind the door lay… another door.
And no one knows what’s behind it or why the original builders would go through all of the effort and expense of constructing these shafts and doors.
Story Credit: Reddit/SitTitsworthEsq