"Nazca lines" made by humans?

In the desert of Nazca (Peru) there is a very strange place, as strange as old, save a great mystery about the Nazca lines for hundreds of years. These figures are geometric lines in several cases, and in others they are human or animal figures, what is impressive is the size of the figures and that can only be seen from an object that can fly or maybe a mountain.
The lines are the testimony of geometrical knowledge of the inhabitants of this beautiful place, were careful not to divert his strokes in over a thousand lines in this place. They could use ropes to make technically perfect lines in the region that extends for over 520 km².
There are over 30 geoglyphs found in Nazca to this day and many show figures of animals, plants and humans with perfect strokes and can only be viewed from at least 200 meters. It is not clear that the method used to perform Nazca people, but surprisingly had geometric knowledge for its time.
A Swiss writer announced them in 1968 in a best-selling book, which explained how the man in the story was visited by beings from other worlds that influenced their culture, another case where theories about visitors from other worlds seem to explain the unexplainable.
There is a line that seems Nazca runway of an airplane, something totally amazing ... maybe visitors from other worlds needed a place to stop at that time? The enigma remains in Nazca, many scientific theory is that the lines are not a runway but are an astrological observatory, so arises the hypothesis that the Nazca people knew of calendars and stars.
If people knew about Nazca seasons and the stars, also knew about astrology, and could do perfect geometric lines of this magnitude, there is no doubt that someone influenced in their culture so they can perform such calculations. The theories seem to explain better the things that happen in ancient times, as the scientific encounters many stone structures on earth with amazing perfection and can not explain it.