< 8000 ft..6. The building skills required to make it are simply amazing.
The granite rocks used to construct Machu Picchu were extremely heavy with some weighing over 55 tons. The stones were either pushed up the mountain by the bare hands of hundreds of men or chiseled from the side of the mountain itself. Machu Picchu was constructed with a technique called ashlar which involves stones being perfectly shaped so that a mortar is not needed. The stones are fit so well that not even the blade of a knife would fit between them.