Machu Picchu

A must-do when on the continent - some people would say it is a crime to visit Peru without seeing the hill-top ruins and I can nothing but agree.
The ruins themselves are well-constructed, numerous and massive but what makes Machu Picchu so spectacular is its isolated setting on the top of a mountain, deep in the Andes, far from any other known civilisation. Imagining how the landscape looked 600 years ago, with no roads or infrastructure, one can wonder what made the founders choose this godforsaken place, far away from everything. And in addition, such a difficult place to erect constructions. Were they smart or were they stupid?
In any case, it is no wonder that no-one managed to find Machu Picchu until 1911.