Quote from _Morpheus:
Consider the most basic facts: the pyramid of giza is 455 tall and made of stone, constructed around 2560 bc. It is a marvel of construction for that time to be sure... also fact: the washigton monument is 555 feet tall and made of stone and was completed in 1888. Why the hell would you think a smaller structure made of the same material couldnt have been made? How stupid are you people? What possible logic do you have for your assertion?
What presently remains of the Great Pyramids are just the cores of the structures. The outer surfaces of the pyramids, which were apparently a limestone mortar, are completely gone. When in their prime the surfaces of the pyramids were smooth and white as snow. Unlike anything the World has ever seen.
Documentaries of the numerous incredible structures in South America are at high altitudes in mountainous terrain. Even with our modern machinery and skills at building, it would be exceedingly difficult to replicate what has been done there. To assume that it was done by humans seems highly unlikely.