Lines in the Desert

I went flying in a 6 seater Cessna plane this morning to see the Nazca lines from above. This is the only way to see them. They are huge drawings made by a pre-Inca civilisation, the Nazca that span several kilometers on the desert's floor. They are amazing. Also amazing is the fact that we can still see them today thanks to the particular desertic climate of the region. Thats is assuming we don't go around destroying them by driving roads through them, which has been done already.

Now something like this, as usual, is the source of controversy. Why did the Nazca draw those lines and how did they do it? Do they have religious significance? Do they have something to do with water, which is scarce in the region? Are they related to halucinogenic cactii? Where they extra-terrestrial landing strips (the Nazca couldn't see their handy work as they didn't have the technology to fly)? I reckon the archeologists forgot about the KISS principle: the Nazca did it because they could and because it was fun.