"The Incas, Kings of Peru, built wonderful edifices, whether fortresses, temples, gardens, palaces, store-houses, roads, or other works. All excelled, as may still be seen by their ruins, though these remains give but an inadequate idea of the complete edifice.

"The grandest and most superb work that they ordered to be built, to show their power and majesty, was the fortress of Cuzco . Its magnificence would be incredible to those who have not seen it, and even those who have gazed upon it with attention, are induced to imagine, and even to believe, that such works must have been completed by enchantment, and that they were made by demons rather than by men. For the multitude of stones, so many and of such size, that are placed on the three circling lines (being more like rocks than stones), excite astonishment and wonder as to how they could have been cut from the quarries whence they were brought. For these Indians had neither iron nor steel for cutting and working the stones.

"It is an equal wonder how the stones can have been brought from the quarry, for the Indians had neither bullocks nor carts. Besides, no cart could bear the weight of such stones, neither could any bullocks draw them...
"Those that came from the nearest point were brought from Muyna, which is five leagues from Cuzco . But to pass onwards with the imagination, and to think how they could adjust such enormous stones, so that the point of a knife can scarcely be inserted between them, would be never to end. Many of the stones are so placed that the point of contact can scarcely be seen...

"The edifices and works which the Incas executed in the form of fortresses, temples, roads, houses and others, were numerous, and required great labour, as may be seen from the ruins that remain at Cuzco, Tiahuanaco, and Tambo, and in other parts where there are stones of immense size. It is difficult to imagine how they cut, drew. and placed them where they now are. A vast number of people must have assisted from all the provinces, in building these edifices and fortresses which the Incas ordered to be erected at Cuzco , and in different parts of the kingdom. The work is strange and wonderful. They used no mortar, and had no iron nor steel for cutting and working the stones, nor machines and instruments for dragging them. Yet, in spite of all this, they are so smoothly worked that, in many places, it is scarcely possible to see the point of junction between two stones. Many of the stones are so large that it is incredible to anyone who has not seen them. I measured one stone in Tiahuanaco , which was thirty-eight feet long, eighteen wide, and six deep. In the wall of the fortress of Cuzco there are many of much greater size. But the thing which most excites astonishment is, that the stones of this wall, though not cut by rule, and of very unequal size, fit into each other with incredible exactness, without mortar...”

(Inca Garcilaso de la Vega. "Royal Commentaries"- translated and edited by Clemens R Markham, C. B. London, 1871)