Saksayhuaman

In the outskirts of Cusco is Saksayhuaman, an elaborate walled complex that among other things really illustrates the construction techniques of the Incas. As is true for most Inca structures there is not much known with certainty about why it was built and exactly what purpose it had. A fortress?, a ceremonial place. This what is in Wikipedia. The name is spelled in various ways and our guide jokingly referred to it as sexy woman.

I like this paragraph found on world-mysteries.com

When the Spanish conquerors arrived first to these lands; they could not explain themselves how Peruvian "Indians" (ignorant, wild, without any ability of logical reasoning, one more animal species according to conquerors) could have built such a greatness. Their religious fanaticism led them to believe that all that was simply work of demons or malign spirits. Still today, many people believe in the inability of ancient Quechuas to create such a wonder, so they suggest that they were made by beings of some other worlds, extraterrestrial beings with superior technology that made all that possible. However, our history and archaeology demonstrate that those objects of admiration are an undeniable work of the Incas, Quechuas, Andean people or however pre-Hispanic inhabitants of this corner of the world would be named.

Here is a Google Earth aerial photo: