(click to enlarge) The stonework at Sacsayhuamán is as fine and precise as at Machu Picchu, and the stones are much larger. Truly a marvel. From Wikipedia:
"Sacsayhuamán ... is a walled complex near the old city of Cusco, at an altitude of 3,701 m. or 12,000 feet. The site is part of the City of Cuzco, which was added to the UNESCO World Heritage List in 1983. It was built by the prehistoric indigenous people of the Killke culture about 1100 AD. They were superseded by the Inca, who occupied and expanded the complex beginning about 1200 AD.
Some scholars believe the walls were a form of fortification. Others believe the complex was built specifically to represent the head of a puma, the effigy shape which Sacsayhuamán together with Cuzco forms when seen from above. There is much unknown about how the walls were constructed. The stones are so closely spaced that a single piece of paper will not fit between many of the stones. This precision, combined with the rounded corners of the limestone blocks, the variety of their interlocking shapes, and the way the walls lean inward, is thought to have helped the ruins survive devastating earthquakes in Cuzco. The longest of three walls is about 400 meters. They are about 6 meters tall. The estimated volume of stone is over 6,000 cubic meters. Estimates for the weight of the largest limestone block vary from 128 tonnes to almost 200 tonnes.
The Spanish harvested much rock from the walls of the structure to build churches in Cuzco. This is why the walls are in perfect condition up to a certain height, and missing above that point. "