Just found an interesting article about mysterious Nazca Lines .

The link above has fantastic pictures taken from airplane.

Direct quote:

"Stretching across the Nazca plains, like a giant map or blueprint left by ancient astronauts, lie the famous Nazca Lines of Peru.

The Nazca Lines are an enigma. No one know who had built them or indeed why. Since their discovery, the Nazca Lines have inspired fantastic explanations from ancient gods, a landing strip for returning aliens, a celestial calendar, used for rituals probably related to astronomy, to confirm the ayllus or clans who made up the population and to determine through ritual their economic functions held up by reciprocity and redistribution or, a map of underground water supplies.

There are also huge geoglyphs in Egypt, Malta, United States (Mississippi and California), Chile, Bolivia and in other countries. But the Nazca geoglyphs, because of their numbers, characteristics, dimensions and cultural continuity as they were made and remade through out the whole prehispanic period, form the most impressive as well as enigmatic archeological group. "