Does not appear to still exist if it ever did. There is no octagonal structure on the Baalbek layout map. There is a hexagonal structure or remains of, called the hexagonal forecourt but nothing is standing, though one fallen, broken pillar looks similar to those in the picture. That structure in the picture looks like it was just set up. After I zoomed in and looked at the base of the pillars my next thought was to look for tracks of a vehicle, though can't make any out. And why is the one pillar tipped out? Was it stood up crooked or did something hit it from the inside?
I don't think that's part of Baalbek, I think its staged. Isn't Baalbek on a hill above the quarry where the other giant stone is? That terrain is flat.