Either these GIANT sarcophagii contain'd ten to twelve foot mummies, or they're just decorations with nothing inside them but structural bracing. Maybe someone out there already knows whether this is a bullshit story or not...
If geopolymerisation existed at one point back in history, when alabaster and granite and limestone could be made chemically as a kind of concrete, then all this talk of AHT or Ancient High Technology is no longer needed - you could cut these 'stones' with a length of wet rope when they were still in their 'wet' or 'unset' state.