This is the famous 12 sided stone in Hatum Rumiyoc Street, Cusco, Peru. It is 1,000’s of years old, carved with a technology long forgotten by man, and is in fact lost to modern science. We do not know how it was done, and we do not know who did it. It wasn’t the Incas. There is simply nothing in their technology capable of achieving it.
The stone is carved from diorite which is a very hard, very rare, igneous rock. These days we cut it with diamond.
Why are there 12 sides? It’s elementary my dear Watson: the most efficient and most conservative means to cut a stone is to remove as little material as possible, just make some flat surfaces so you can get a good seal with other rocks (there is not filler or mortar used in this wall). This is only possible if the means by which you cut the rock is so easy, is so simple, that you do not mind putting in 1, 2, 3, 12 sides to get fit you want. Cutting rock almost as hard as diamond like a hot knife cuts butter – what reality is needed to achieve that?
That is another discussion, and includes the Pyramids, and Florida’s Coral Castle – a very, very recent application of a similar and related technology.