Machu Picchu sits high in the Urubamba Valley of Peru with precipitous drops all around that can dizzy the head in a way that has nothing to do with the nearly 9,000 ft. elevation. A great deal of mystery surrounds the site because nobody can truly explain why the Incans built it. Fortunately, that lack does nothing to prevent appreciation for the small city's craftsmanship, exemplified in the Incan's ashlar style of construction in which blocks of stone are fitted together without mortar yet are secure enough that a knife's edge cannot penetrate the cracks.