that 200-ton wall in Cusco where a paper won't slide between the blocks — ok how

Been chewing on Saksaywaman (Sacsayhuaman, however you spell it) for a while and I still don't have a clean answer. For those who don't know — big zigzag walls above Cusco, Peru, blocks up to ~200 tonnes, polygonal, like 12 sides on a single stone, and they're fitted so tight you genuinely cannot ge……