The Secret of Machu Picchu
When Hiram Bingham discovered Machu Picchu there was many things that puzzled him.
One was that the site did not seem to have enough land to support many people. Another was that there were no elaborate tombs containing gold objects or precious jewels. He only found very simple tombs. And finally there was very little evidence of glass, tiles, nails or anything else that were introduced by the Spanish. That at the very least led him to believe (correctly) that the Spanish conquerors were unaware of Machu Picchu.
But why would the Spanish, who made detailed maps of all of their lands not be aware of a place that was only 3 days journey from the Inca capital. One of the reasons may have been that because there was no gold, silver or jewels there the Spanish were not interested. Another reason is that is that it may have been abandoned (perhaps because of disease) before the Spanish arrived and not re-used by other Emperors.