I am neither an archaeologist, an anthropologist, an historian of pre-Columbian civilizatins, nor an art expert. However, I’ve come up with a theory that has baffled all of the above, relating to the Nazca lines.
Apparently no one knows how or why the Nazca managed to build them (they’re only fully visible from the air, and the Nazca obviously didn’t have aircraft). And, of course, why did they build them in the first place? No one at the time could see them.
Well, I’ve figured out how AND why. We’ll deal with the why first.
The Nazca must have believed in tribal gods, as did most (if not all) pre-Columbian Amerindian civilizations. Believing that at least some gods dwell in the heavens, then the Nazca obviously made those giant patterns to be seen by the gods up in the sky. Simple enough. And the Nazca desert is the perfect canvas for giant works of art, viewable only by divine beings.
So how did they do it? When I was a kid Mammarasta used to buy me these “fun books” with lots of games and puzzles in them. One of the activities was a “Draw It Yourself” exercise; a professional artist would draw a caricature (say, a lion licking a lollipop) on one page and on the facing page I was to draw the same scene. The trick was that each page had a grid on it. One the one page the grid was superimposed over the image, and on the other the grid was on a blank page. These grids broke the image into smaller, reproducible parts. In other words, section c7 of the image grid only had a couple of wavy lines; and on my blank page I could easily reproduce those wavy lines. When combined with the images in sections c6, c8, b7, d7 and so on the simple, easily-reproducible lines I was drawing would have formed the coherent image on the facing page. An image I could have never drawn on my own. Am I making sense here?
So, getting back to the Nazca… Refer to the monkey (or is it a spider? who can tell?) at the top of the page in the link up above. Let’s say that a Nazca Artist (we’ll call him “Bud”) drew that image on an animal hide or whatever he had handy. Along comes a Nazca Architect (we’ll call him “Lou”) to draw a perfect 20 X 40 section grid over it. He then consults with a Nazca Mathmetician (we’ll call him “Larry”), who determines that each square section of Lou’s grid on paper will represent a one-meter-squared section on the ground (let’s assume that the Nazcas used the metric system :D). So, a Nazca Surveyor (we’ll call him “Sam”) then goes out to the desert and, with his crew, builds his grid. Using ropes, posts, and a measuring stick, within a few days he has his grid on the ground (let’s assume that the Nazcas knew how to make perfect right angles and straight lines). Now, all that’s left is for the Nazca Ground Scratcher (we’ll call him “Mack”) to scratch the ground and make the lines, one section at a time, using Bud & Lou’s schematic. Once he’s done each of his ::does math:: 800 sections, Sam pulls down the ropes and posts. Then Bud, Lou, Larry, Sam & Mack all admire their work. Of course, they can’t actually see it so they’re basically just hoping it worked. Two thousand years later, some dude in a Cessna flies by and says, yes, by golly, it worked.
So there’s my theory. Either I’m a freaking genius and I’m going to publish it and make huge stir in the archaeology world, or I’m a raving idiot and the good people of the SDMB are going to shoot my theory full of holes.
Go ahead, I can take it! 
