Egyptians stacked blocks of stone to build the pyramids.

Roman concrete was impressively strong.

Neither of them had steel-reinforced concrete.

Neither did Gothic cathedrals, which is why they needed flying buttresses.

Reinforced concrete as we know it today is a 19th century innovation, as I understand it.

en.wikipedia.org/wiki/Reinforced_concrete?wprov=s…

Maybe the commenter was thinking of adobe.