The Inca ordered that the provinces should provide 20,000 men and that the villages should send the necessary provisions. If any fell sick, another labourer was to supply his place, and he was to return to his home. But these Indians were not kept constantly at a work in progress. They laboured for a limited time, and were then relieved by others, so that they did not feel the demand on their services. There were 4,000 labourers whose duty it was to quarry and get out the stones; 6,000 conveyed them by means of great cables of leather and of _cabuya_[202] to the works. The rest opened the ground and prepared the foundations, some being told off to cut the posts and beams for the wood-work. For their greater convenience, these labourers made their dwelling-huts, each lineage apart, near the place where the works were progressing. To this day most of the walls of these lodgings may be seen. Overseers were stationed to superintend, and there were great masters of the art of building who had been well instructed. Thus on the highest part of a hill to the north of the city, and little more than an arquebus-shot from it, this fortress was built which the natives called the House of the Sun, but which we named the Fortress. The living rock was excavated for the foundation, which was prepared with such solidity that it will endure as long as the world itself. The work had, according to my estimate, a length of 330 paces,[203] and a width of 200. Its walls were so strong that there is no artillery which could breach them. The principal entrance was a thing worthy of contemplation, to see how well it was built, and how the walls were arranged so that one commanded the other. And in these walls there were stones so large and mighty that it tired the judgment to conceive how they could have been conveyed and placed, and who could have had sufficient power to shape them, seeing that among these people there are so few tools. Some of these stones are of a width of twelve feet and more than twenty long, others are thicker than a bullock.[204] All the stones are laid and joined with such delicacy that a rial could not be put in between two of them.