nostalgia

How can someone feel nostalgia for a time that they didn't even know??
Che Guevara spoke about this in his book the "Motorcycle Diaries". He felt nostalgia for the Ancient Aztec people of Latin America when visiting the ruins of Machu Pichu. I guess he was talking about the way things used to be... people as one. He wanted all of South America to be united and the Aztec people were united across the Continent. But what about the Incas? weren't they there too? I guess it's more about how the Spaniards invaded and completely destroyed the ancient culture and society of the land. But Che had to have some form of Spanish blood in him. While i know that the Spaniards did a terrible thing by murdering tons of natives and ruining their culture, does he not feel nostalgia for the Spanish culture that has to be part of him in a way?
Anyway this rambling comes from me feeling nostalgia for the 1960's. I never lived during those days, and while i've taken classes and read tons of books on the era, i can never really know what life would have been back then. For all i know i could have been an incredibly boring person who didn't listen to any of the music that i iconosize about this era. I will never know. and it's hard to hold an era on a pedestal when you have no way to know whether it is worthy of it.
Just a thought