The Real Location of the MISSING CAPSTONES?

Of the Giza Pyramids?

The Giza pyramids seem to have some capstones which have simply gone missing! We do not know where they are. Nor do we know if they ever even existed, appearing to have never even been built into the structure. OR, did the East Roman Empire (Roumania), bring them to Byzantium, to be placed in the middle of the Hippodrome, along with various other monuments? That would make some sense. They appear to be depicted on a drawing of the city, though of course they are no longer to be found there.

IS this where they are, Istanbul?