A triangle within a triangle pointing at a triangle??? Triangle inception? a prank, an ancient pointer? Sounds like some Indiana Jones sorta stuff right???
The top of a pyramid? maybe it could have once been a ship docking point? or maybe under the triangle is a bigger mystery?
Or could this Triangle possibly be an ancient switch to turn off the flood tunnels? But with so much diging and damaging of the original system, maybe this switch may not work anymore?