I did my “Quarry Project” about 25 years ago, and while working on Crotch Island I paced off a block of granite 10 x 12 x 15 feet which I calculated to weigh about 720 tons. Those quarrymen had black powder, compressed air/kerosene burners, and the largest front-end loader I’ve ever seen.
The Incas and their predecessors had none of those tools but were able to quarry, transport, cut, fit and finish granite or rhyolite blocks that weighted up to 100 tons. We can only guess, and there are some well educated guesses out there, as to how they did it. There are also some really crackpot ideas involving aliens, and cast-in-place molten granite. Right.
What is known, and the experts are fairly sure of this, is that they did not quarry the stone like in Maine, but climbed high in the mountains to find stone already broken apart, rough-sized the blocks, slid them down the mountain, stacked them on one side of the river, then changed the course of the river so the stone was now on the other side, then skidded the blocks to the constriction site. Except the site was way up another mountain, so they built a ramp to get them up. The stone is fairly easy to shape with the correct-size hammer, made from a harder rock, when struck at the proper angle. What is still not known is how they lifted them in place, and lowered, then lifted, then lowered and lifted over and over to get the perfect fit. But they did.
Today we hiked about halfway up the mountain above Ollantaytambo, a small town on the river and the last stop before Machu Picchu. The ruins are both pre-Incan and Incan, but I can’t tell the difference. Some say this site is the equal of Machu Picchu, but I guess we’ll have to wait a few days to find out. Early departure allowed us to avoid the other tourists, to get great morning light and to avoid the strong winds that come up every afternoon. Perfect day.