Respuesta :

Question: What is Machu Picchu? 
Answer: An Incan citadel that's located in the Andes Mountains(Peru) 

Question: When was it discovered? 
Answer: Well Machu Picchu was built sometime during the 15th century.  Hiram Bingham re-discovered the 'lost' city on July 25th, 1911. 

Question: Why did it take so long to discover?
Answer: Honestly, I don't know. Probably because no one even knew about this city lol. On his travels, Hiram was told by a villager that there were some ruins. Also because of its location, I figure. But I'm also sure it's because no one knew of its existence except for the people living by the ruins. Not even the Spanish Conquistadors knew of Machu Picchu, so it was never written down. NO one really knew.