Under our noses for centuries, the Nazca Lines were finally re-discovered in 1927. Massive etchings in the Peruvian desert floor, the lines form the shapes of animals such as a monkey and killer whale. Only noticeable from nearby hilltops or while flying overhead, some of the shapes stretch for over 660 feet (200 m), and some of the lines for over 5.6 miles (9 km). Though we’re still not sure why they exist, it’s believed they served a religious purpose.

In the Peruvian Desert, about 200 miles south of Lima, there lies a plain between the Inca and Nazca (sometimes also spelled Nasca) Valleys. Across this plain, in an area measuring 37 miles long and 1-mile wide, is an assortment of perfectly-straight lines, many running parallel, others intersecting, forming a grand geometric form. In and around the lines there are also trapezoidal zones, strange symbols, and pictures of birds and beasts all etched on a giant scale that can only be appreciated from the sky.

The figures come in two types: biomorphs and geoglyphs. The biomorphs are some 70 animal and plant figures that include a spider, hummingbird, monkey and a 1,000-foot-long pelican. The biomorphs are grouped together in one area on the plain. Some archaeologists believe they were constructed around 200 BC, about 500 years before the geoglyphs.

There are about 900 geoglyphs on the plain. Geoglyphs are geometric forms that include straight lines, triangles, spirals, circles and trapezoids. They are enormous in size. The longest straight line goes nine miles across the plain.

How were they built? The lines were apparently made by brushing away the reddish, iron oxide covered pebbles that compose the desert surface and uncovering the white colored sand underneath. In most places wind, rain and erosion would quickly remove all traces of this within a few years. At Nazca, though, the lines have been preserved because it is such a windless, dry and isolated location.

A writer by the name of Jim Woodman believes that the lines and figures could not have been made without somebody in the air to direct the operations. “You simply can’t see anything from ground level,” states Woodman. “You can’t appreciate any of it from anywhere except from above. You can’t tell me the Nazca builders would have gone to the monumental efforts they did without ever being able to see it.”

Woodman has proposed that ancient hot-air balloons were used to get an aerial view of the construction. To prove his hypothesis, Woodman constructed a balloon using materials that would have been available to the Nazca people. He was able to conduct a successful flight, though it only lasted two minutes.