Stone works of unreachable precision is South America

The Inca stone-builders in Cusco and Ollantaytambo show an incredible
precision in the working on stones.

According to science, the Inca civilitation didn't know about metal for working stone,
no wheel and no writing. Were the flat surfaces created with materials such as sand,
water, hard rock, and through cumbersome attrition!?
....Anyone can believe this.

How the stones look, with remains of "pivots"
and patterns, increases the suspicion that
a special type of concrete could have been used here.

The fortress walls of Sachsaihuaman above Cusco show the same building style
with a small difference that here the stone blocks are up to 9m high
and weigh over 300 tonnes!

...large, larger, largetst.

The quarry was located kilometers away, and the problem
of transporting the huge blocks remained.
Even today only assumptions exist on why was the complex built
and who its builders were.

A rock formation lies nearby.
How this hard rock was worked upon remains still an mystery.
The tools that the archeologists assign to this civilization
were not good enough to produce such precise incisions.

The incredibly exact stone works can also be seen at the Inca fortress Machu Pichu.