In the Amazon rainforest, there are miles of raised mounds forming lines in the middle of swampy land, thought to have been used both for agriculture and as roads by ancestors of the local Amerindians.
Maybe the Nasca lines makers were just their more artsy-fartsy cousins, and at that time the desert was more fertile. After all, Caral is considered to be the start of civilization in South America, and is now desert. So too with Egypt, even though when Egypt started, the country was wetter.
Just sort of joking. The Nazca lines are intriguing not only because of their extent, but also their shapes.
Here are some links, in any case, but without pretty pictures:
and a Wikipedia one:
I have read all of the links you posted; I have not read about this previously. It implies a much more active population in that part of the amazon in the pre-colombian era. In some cases they appear to have had some sort of dual-functions, if I read correctly.
and before the Inca (and just about anyone else since there are no earlier written records?) there were the Sumerians
whose drawings and descriptions depict figures that also look remarkably like “astronauts” or other world vistors, certainly their “gods and goddesses” came from the sky
http://www.crystalinks.com/sumergods.html