The world was not aware of Machu Picchu until 1911 when a professor from Yale named Hiram Bingham, who later became a U.S. senator, stumbled upon it while he was looking for another site altogether. It's interesting to note that other "lost cities" like this lie nearby in an overgrown and unexcavated state. Peru simply cannot afford to excavate all of it at this time.
Over 100 skeletal remains were excavated at Machu Picchu, and, curiously, 80% of those were female. A great deal of speculation about the purpose of the site has resulted from that fact alone.
There are many ornamental rather than practical sites, and combined with the significance of having such a dynamic location, it could have been an important ceremonial site.
The name itself means Ancient Peak, and the neighboring mountain, Huayna Picchu, means Young Peak. It is curious that the Spanish had no knowledge of it, which leads to the conclusion that the Incas had no knowledge of it, either. Because they were known for wiping unfortunate details from their records, it is possible that for some reason the population was destroyed and all records officially erased.
The structures on the site indicate a permanent population of around 1000 people. Because there is a large amount of agricultural terracing, it is likely that this community also met the needs of a much larger population.
Archaeologists have hypothesized that a main purpose of Machu Picchu was to provide a steady supply of the coca leaf to the royals at Cusco.
All evidence seems to point to the fact that the buildings' purpose was not strategic.
The site of the Three Windows might actually be a site called Tampu-Tocco, a legendary place where the kings of Cusco would seek refuge. These windows are exactly aligned so that the sunrise could be seen through all three of them on the days of the winter and summer solstice. The windows are significant, because no house in Cusco had any windows at all during the time that the Inca civilization flourished.
