Saksaywaman's fortress walls aren't the only inexplicable sight in Peru. There's also the Nasca Lines to think about. They're a collection of more than 100 carvings in the earth of the desert, dating back 2000 years. The majority of them are drawings of animals.
The most confusing thing about them is that they're too large to be seen from a standing position - you'd have to be passing over them in a plane to get the full effect. How did the Nascans even make the drawings when they couldn't see what they were doing?