It wasn’t until the 1930’s, when airlines began flying overhead, that passengers first noticed the unusual lines and drawings cluttering the landscape below them in the Nazca desert of Peru.
Warranting further investigation, it was revealed that these designs were simply made. It involved brushing the reddish pebbles and rocks from the desert floor, which would reveal the white colored sand underneath. Because of the lack of rainfall and dangerous winds, these drawings had remained unaltered and could very well be centuries old.
In fact, pottery remains found near some of lines were were carbon dated to 2,000 years old. 

What perplexed the scientists and researchers was why these lines and drawings were made in the first place. For one thing, their beauty could only be seen from the air and no reasonable explanation could be identified.
It wasn’t until Paul Kosok, an American historian, arrived on scene in 1941 that provided a possible reason for these designs. His most favorable explanation; that they were used as an astronomical
observatory was eventually proven false. In 1968, Gerald Hawkins, an astronomer/archaeologist who had helped identify Stonehenge as an astronomical observatory, conducted an analysis of these lines. He determined that only 39 of the 186 lines matched astronomical positions. This proved that the lines must not have been solely designed for astronomy and must have had some other purpose.
Theories such as the lines have religious meaning and connect irrigation systems to places of worship or that the drawings of birds and other animals were intended to produce rain fall have also been brought to the table.

 But as of today, there has yet to be a logical explanation for these strange lines and drawings, created many centuries ago, that can only be appreciated from thousands of feet in the air.
References: The Nazca Lines, Unsolved Mysteries of History, Nazca Lines and Cahuachi Culture

