Theories abound regarding these mysterious etchings, ranging from landing strips for aliens to a giant seismograph. The most probable theory is that of María Reiche, a German researcher who dedicated her life to studying the lines. Ms Reiche believed that the lines were part of a vast astronomic calendar whose figures marked different solar phases. Ms Reiche, affectionately nicknamed the Angel of the Plains by the local inhabitants, was the first to discover the ancient technique of digging into the tough and dry desert floor and covering the track with stones brought from distant sites. The component of natural plaster existing in the area helped to preserve for thousands of years the drawings: the hummingbird, the spider, the condor and the monkey, among the more than 30 figures etched into the plain.