It is not only an engineering and architectural marvel, but its location high above the Urabomba River Valley must have posed tremendous logistical challenges to its construction.
As testament to its difficult and remote location, Machu Picchu was not discovered by modern man until 1911. And its founder, Hiram Bingham, likely had help from local natives of the area. 
Historical and archaeological evidence indicated that the complex was constructed and inhabited for no more than about 90 years - 1450 to 1540. Fortunately, it was never found and destroyed by Spanish conquistadors as were many other Inca Empire cities and fortresses.
The intricacy and preciseness of the stonework are a sight to behold and are unsurpassed anywhere else in the world. Even today, it is difficult to impossible to match the precision with which this ancient culture constructed this and other Inca buildings. 
Llamas are common among the ruins and do a great job of keeping the grass and other vegetation at manageable levels in areas that would be difficult to access with machinery.
Our first day at the site was partly cloudy to sunny. But clouds, rain, and fog moved in overnight and we awoke to what was probably a more common weather pattern for this high elevation in the mountains. 
But the fog and mist shrouding the adjacent mountains and parts of the complex added a surreal and mystical aspect to our visit. 
As we headed down the mountain on the single lane access road (with 13 switchbacks), 
I had a sense of fulfillment in finally experiencing this magical place that I had first set sights on visiting 45 years earlier. And I also felt grateful for how fortunate I was to be able to visit Machu Picchu, one of the most magnificent places on earth.Oh, you were wondering about birds! I did do some looking and saw some good ones, but taking in the marvel of this place occupied most of my time!
