correct me if wrong but i heard the romans removes the limestone or other material from the piramids and taken to rome,not the big stones,but something like tiles on the outside of the piramid,someone with better knowledge will explained better.
Virtually all of the stone in Roman construction -- both structural and cladding over brick or rubble core -- is travertine, quarried in the suburban village of Tibur (modern-day Tivoli).