|The reason why Machu Picchu was so famous was because of Hiram Bingham who found the lost city in 1911. He wrote an fascinating story about the "lost city of Incas" (it was supposed to be an archaeological report).|
Machu Picchu was surrounded by roughed, inaccessible mountains. The ruin was kind of intact. Bingham said it was never found by the Spanish and it was a secret holy city or a "lost city". But it's actually more of a "abandoned city" than a "lost city". Some archaeologists said that the Spanish did record the existence of Machu Picchu. The Incas set fire on the city when the Spanish came. And the fact that most "holy city" in the world are usually not very "secret" makes Bingham's report seem doubtful (if it's secret, how can you market your religion?).
But still, something remain very secretive in Machu Picchu, e.g. 70% of the human remains found in Machu Picchu were females. And there are lots of interesting gimmicks around the city.